A friend of mine had similar dilemma in her bedroom with a solution that I absolutely adore. She painted a monotone abstract floral graphic using a stencil above her bed instead of opting for an actual headboard. Other options could be using stick on graphics which might be a less permanent solution and still on the cheap.

i really like it the way it is. if i was wanting some more pizazz, i would probably go with a mobile, like these
http://www.etsy.com/shop/thewonderlandstudio

A nice graphic print? I am sure you could find something on etsy you like. Maybe something typographicy?

Some art would be nice. Either one large piece, or a few small pieces. On a separate note - if those doors to the side are closets you need access to, you might try removing the doors (stow under the bed or use elsewhere as a tabletop) and put up curtains for easier access.

i actually really like it the way it is. i would say maybe paint it in a color that maybe you like better?

anything too loud or busy will seem tacky in a "hey i have no idea what to do over my bed here" kind of way. if you have to have something - think paint - maybe look at Mark Rothko paintings and DIY something inspired by those.

Wallpaper if you can, or use the fabric and starch trick.

I like the Lotta Jansdotter's wall stencils from Chronicle Books and I also saw on Amercian Pickers (The History Channel, I LOVE that show!!) those cool old architectural letters. Maybe one HUGE letter would be cool and hang it off center?

Find something cute to hang, like a string of stars [http://www.tenthousandvillages.com/multicolored-star-valance] or a big fun travel poster.
Or get a close-up photo blown up to poster size, like a giant flower or ripples on water. That would be neat. : )

I like how defined the area already is. Perhaps add a mirror or a framed textile.

There is always a headboard wall decal! lol Also, I totally agree about removing the closet doors for easy access.

You could always go with tacking ribbon to the painted space. I'm not talking frilly, but neatly tacked ribbon in a pattern (all one direction, crossing each other, basket-weave, whatever you prefer) within the moulding. It would be a cheap, bold (or not so bold, depending on the direction you go) solution that would be all your own with respect to color, pattern, texture, etc.

Just a blank white canvas.

This looks like a child's bedroom. The poster, Curious George stuffed animal and bedding combined with the baby blue wall have already given the space a "theme" so you need to think about how you want to proceed from there. Is this your style or do you want something a bit more adult (I'm assuming you are an adult)?
Some people mentioned wall applications, which I personally would stay away from if you are deciding to make it look more grown-up. Stencils can be tricky. My immediate inclination was a large piece of artwork. Perhaps a world map? I also like the idea of something more graphic in minimal colors (like B&W) but I think navy blue would look good too.

I like the idea of a round mirror...

something like this (sorry for the ugly link): http://www.pier1.com/Catalog/HomeAccentsD%C3%A9cor/HomeAccentsDecor/tabid/508/CategoryID/134/List/0/catpagesize/25/Level/a/ProductID/5503/ProductName/Round-Shell-Mirror/Default.aspx

That's for all the input everyone! These are all awesome ideas. I hadn't even thought about removing the closet doors - the one in the back especially is really difficult to get into so I just don't keep much int here.

Not sure you need to do anything at all, but perhaps something small? I hung a vintage wall lamp above my bed, so it's both decorative and useful:
http://farm5.static.flickr.com/4153/5198337393_0e195574d8_z.jpg

I like it so far and don't think it is too childish. I love artwork over a bed. You can go with a collection of art or just a few pieces. Check out sfgirlbybay's website. Just today she posted some suggestions for hanging art. I think she got her images from the online mag Lonny, which also provides lots of eye candy.

hang a pastel mosquito net and let it fall down the back sides for a romantic look; a string or drape of fairy lights for a bit of fun or maybe a living indoor garden wall eg.
http://www.woollypocket.com/wally/wally-one/
http://www.modcloth.com/store/ModCloth/Apartment/Furnish+Decorate/Stunning+Stampede+Light+Set
http://www.modcloth.com/store/ModCloth/Apartment/By+Sea+String+Lights
http://www.ikea.com/au/en/catalog/products/90198761
http://www.ikea.com/au/en/catalog/products/40198805

I like it the way it is, but a nice framed piece of artwork would be nice...
...just be sure to get something that doesn't appear cheap, like a poster - a real oil painting in a gilded frame would make the place so much more interesting and sophisticated.

But dont' remove the door to the closet - as awkward as it may be, who wants to look at clutter and mess when you're in bed?

one large piece of black and white art

@WhiteonWhite Thanks - I don't really either. Plus the bedding isn't always just the solid colors.

@MelisaDickson Thanks! Those are great ideas. Esp since I'm in an apartment - investing time or effort into something I can't take with me doesn't seem fun.

photo collage!

I really like the idea that the wall is decorated to act as the bed head… I think you should expand on this concept as it is very simple and very effective. Perhaps you can install another moulding on the inside of the existing one in the shape of a smaller bedhead painted white to break up the blue. I think the perfect shape would be square with inverted top corners approx. 180mm x 180mm… I hope that makes sense. You can buy moulding lengths from most hardware stores, all you would need to do is cut them to the right size (ensuring they have mitred corners) paint them white and glue or nail to the wall.

a floating shelf with pictures/books.

How about a few decorative, white (or spray-painted white) picture frames? I think they would be simple enough to let the color "shine" but would add some interest to the wall. You could also hang something inside the frames if that's too simple for you!

Chalkboard paint! You can't constantly change what's back there.

Keeping it simple. The painted wall looks like a headboard. Add a bit of architectural interest by installing small Tolomeo (Artemide) wall lamps on each side of the bed. http://www.designer-lights.com/products/images/artemide-tolomeo-mini-wall._48626ba5.jpg

And if you want to add a piece of artwork, select something soothing, simple and elegant. The MOMA sells beautiful Mark Rothko prints. http://www.momastore.org/museum/moma/ProductDisplay_Rothko%20Untitled,%20Framed%20Print_10451_10001_57247 Stunning.

Check out my blog for an answer. See under "Bedroom Secrets" at
http://mikis-design.blogspot.com/
I did a Braille Wall as headboard.

how about a panel of lights, like ones from IKEA?

@ sdfdawe and yessoso.com:
try to keep your spam off peoples' pages
it's really desperate and junky.

Don't know if this was already said (because I'm too lazy to check), but I had a big empty space like that behind my bed. I hung a curtain rod and some light, flowing curtains in that spot. It's great because you can switch out the curtains for a new look. Good luck!

Your room reminds me of the bedroom on the blog YellowBrickHome. They did a small picture ledge with a couple of modern prints. Check it out...
http://www.yellowbrickhome.com/our-sweet-home-chicago/

I'd suggest a collection of small mirrors, in ornate frames. Flea markets and thrift store finds. I'd also see if the landlord could possibly rehang the closet door so it opens from the other side.

Have lived in many Brooklyn brownstone apartments, so it isn't that I don't like the old brownstone wood trim - I love it. But this is clearly a doorway, one that likely had french doors originally (if that wood trim above the bed is original.) Anyway, to me it is a problem (in my intuitive sense of what is good feng shui, which is what makes me feel good, if not in the actual feng shui, though it may be there as well) to have a bed against a doorway. I've gotten really good ideas in the past by reading what feng shui books have to say about placement of bed and solutions, and about the need for a strong headboard - I find in those areas, it doesn't steer you wrong.

So, my take would be to cover the doorway with a curtain. But not a light flowing one, as someone suggests, but rather a darker, heavier looking one - to give the headboard area some strength. Would look really nice I think - better than a painted filled in doorway.

If there is room for the curtain to hang behind that radiator, that is - I can't tell from the picture how close it is to the wall. If not enough room, then I'd paint the entire back wall one color, to call less attention to the doorway, and then hang whatever you like on the wall.

Another alternative, and one that lets you preserve the doorway look, while filling the doorway with doors, would be to find some old doors that fill the blue space and lean them (or affix them to the wall if necessary) - I don't mean brownstone type doors, though that could work - I'm thinking those room divider panels that are exotic carved woods, with or without holed in them. Sometimes you see these as old carved doors in antique stores. Or old wrought iron gates. Something along those lines. A different look than a fabric curtain, but also something that would close the doorway visually, which the drywall (or plaster, depending on when it was filled) doesn't do for me visually.

I've always wanted a wrought iron bed, I would paint a "headboard" on that wall. It would be very elaborate, and "fancy up" the conservative space!
And yes, take down the closet doors, replace with a curtain.

Needs large artwork.

I'd pick canvas (painted, or photo printed), but even framed artwork would look good here.

Paint the entire back wall the same color. Center over the bed a single large framed landscape of where you'd love to be--great for unwinding and sweetening dreams.

Mural, tapestery, a framed piece of art, etc. There's tons of ideas.

I think a piece of framed artwork with bold color would be nice.

Just inspired by a new AT post on creative re-purposing of doors. Take the closet door off and use it as a headboard!

If you like bold colors (like on your bed, which seem to kind of match the monkey colors), then maybe a deep wine brown color frame (with some art) or a large wooden art object might be best to try and warm up the space. All those white doors and the other white walls are kind of cold. I like dark wood in bedrooms to make me feel cozy.

In my guest room, which is headboard-less, I hung two large paintings. You could DIY your own with some blank canvases (I did for my own bedroom!). Art supply stores even carry really long, narrow canvases you could mount horizontally. If you paint it yourself, you could paint an abstract that's more muted so there's some texture but not loud colour. You can even use a palette similar to your wall colour and surrounding decor.
~Tanya
dans-le-townhouse.blogspot.com

I always love the look of a sunburst mirror.

I think that painting the trim the same color would make it feel more like a headboard than a filled in archway. You could also add a bit of surface molding within the space above the bed - a rectangle or series of rectangles painted the same color - which would give it more of a woodwork look, similar to the panel door headboard in this post.

Also, I think that artwork would be a very good solution. My first instinct was to suggest that you get two or three canvases and paint them as a set with intersecting geometric shapes in the colors of your bed linens.

The colour of the headboard wall reminded me a lot of Carrie's bedroom from Sex in The City. Don't know ifthe set you love or hate the show/movie, you have to admit the configuration the designer used in her bedroom is easy to make your own.

http://www.blogcdn.com/www.shelterpop.com/media/2009/06/new-line-cinema.jpg
Or
http://4.bp.blogspot.com/__wblanPewTU/SDObwFlyoUI/AAAAAAAAA3U/5lanhotnDKs/s400/carrie_bedroom.jpg

Depending on your taste, you can put prints of paintings, black and white photographs, drawings, or family photographs into frames. Or if you want to use antique books as decor, you can put in some shelves with sconces.

There are so many directions you can go. It depends on your style. Do you want bold or do you want warm?

rectangular mirror with red painted frame. boom.

a large black and white architectural photograph preferably on canvas. stay away from glass-covered frame if you know what i mean...

I think a starburst mirror would look great there.

I bought a wall decal from an Etsy seller and used that to decorate the space above my bed: http://itsagreengreengreengreenworld.blogspot.com/2009/09/shanickers.html

"Hang the monkey." LOL

i like the look of a big piece of artwork, preferably canvas. if you're going to stick with the light blue and browns perhaps a piece of artwork with mainly those colors (or whatever others you chose) but with with touches of contrasting/complementing colors, like a saturated orange or peach.

ANTLERS

Great post!