Put your couch in the center of the room (facing away from your bed), where you would like your "wall" and then add a dress curtain or room divider (something like this http://www.ikea.com/us/en/catalog/products/70182191/). It will make it appear as if your couch is against another wall. The room divider isn't very clunky so you wouldn't lose much space.

Expedit. It's cheap, it's sturdy, and it provides extra storage and privacy for studio dwellers. Buy one or two and put them on their sides to form a low wall along the length of the bed.

IKEA's Expedit shelving is cheap and functional, as it adds a lot of storage. If you want a solid division, you can add boxes instead of using it as shelving.

I like the big Ikea expidit as a room divider. I've seen it used in a few open concept spaces. This turns out to be an AT image. I googled it...

http://i-cdn.apartmenttherapy.com/uimages/la/040309book-06.jpg

You can purchase backing material at the big hardware stores and they will usually even cut it to size for you. Here's another image from AT with a backing attached...

http://i-cdn.apartmenttherapy.com/uimages/sf/5-04-08expeditretro.jpg

Have fun doing up your new place!

Ikea sells these privacy panels that operate on a track that you can hang from the ceiling. So you can close them for simple privacy but open then up in the day time for a more spacious feel. I echo the Expedit suggestions above. From a storage standpoint they are wonderful. Easy to put together and come in some nice colors that will add pop to the space.

Turn your bed in the corner that it is already in (so that the headboard is under that window). Then the clothes racks could go along the side of the wall near the closet at the end of the bed. Expedit shelving could go at the side of the bed as a room divider and you'll have the whole other section of the room to create a living room area. Bonus is that you will have a window in each "room" area, making them feel more open and separate.

Another idea is to use that existing clothes rack as a divider int he same way that the bookshelves would be used. Hang your dressy and colourful clothes on it to add interest.

You know what would be really cool ... If you had five or six old doors, you could hinge them all together, paint them & attach strips of carpet to the bottoms of them to prevent scratching up your floor. If the doors turned out to be impractical, you could use something else ... http://rustiques.blogspot.com/2010/10/old-door-room-divider.html

I think floor to ceiling curtains are a great way to separate the sleeping area. You can put them on a track attached to the ceiling. I have a studio but it's too small and awkward to do this, so I have my bed against the wall. Also, area rugs are a great way to visually separate areas. Also, I came across this gorgeous studio yesterday http://theeverygirl.com/feature/nikki-rappaports-washington-d-c-studio-home-tour/ - I just love the way it is arranged.

The clothing rack you have there (if they are yours and you plan to keep them) would make a great divider. Like the commenter above said, use them to divide the "bedroom" corner from the rest of the space. You can simply cover the rack with a fabric cover or be creative and use paneling of some sort.

As for placement of the bed, you have several options: Facing the closet, facing the racks, with the headboard against the racks. Try them all and see which feels best to you.

Check out this beauty: http://www.apartmenttherapy.com/how-to-build-a-sliding-door-fo-139922

Another option is an Ikea curtain cable and hooks they provide onto a colorful sheet.

When I lived in a studio I used a couple of mid-height billy bookshelves to divide the space. I placed my headboard up against the back of the bookcases. This had two functions - it covered the ugly fiberboard back of the shelves, and the shelves acted like a wall to suppost the headboard.
I liked the mid-height shelves as it provided enough of a visual barrier between the two spaces that you couldn't see my bed, but they didn't block any of the light coming from that side of the room. I also like the Billy shelves as they're a little less deep than the Expedit which is good in a small studio space.

Floor to ceiling curtains. Ikea has the DIGNITET system -http://www.ikea.com/us/en/catalog/products/60075295/ used in conjunction with the DIGNITET corner fixture -http://www.ikea.com/us/en/catalog/products/40078030/

I used white bed sheets and hung them from the curtain cable using the RIKTIG clips from Ikea. Its all really inexpensive to put together and softens the space while making everything cozy and intimate.

http://www.ikeahackers.net/2010/12/funky-pax-room-divider.html

The IKEA pax wardrobe (though a little on the pricey side in my eyes) is a GREAT solution for this. It gives you TONS of wardrobe storage in your "night" area, and with some fun fabric, creates a "wall" to anchor your "day" area. :D I used this same idea in my studio for years.

http://community.apartmenttherapy.com/contests/smallcool/2012

http://community.apartmenttherapy.com/contests/smallcool/2011

http://contests.apartmenttherapy.com/2010/small-cool/

I've currently got an Ikea Stolmen system (www.ikea.com/us/en/catalog/categories/departments/bedroom/19109) as a partition between my bed and living areas. It's a bit intensive to install, but I wanted there to be a defined separation all the way to the ceiling while still letting light through, as well as useful storage, and it's provided that for me.

I don't have a picture, but it's essentially set up like this (including the TV on a turntable): http://singaporebrides.com/articles/wp-content/uploads/2011/04/STOLMEN-Storage-solutions.jpg

I added some drawers to the bottom half to use as a dresser. When my dad helped me set it up, he screwed the top of the poles into the ceiling, which will be easy enough to spackle when I eventually move out, and left the floor ends unscrewed. It's been three years and has held up pretty well. I had considered an Expedit, but didn't want something so hulking in the middle of my apartment, and I'm glad I went this route - it was an expensive initial investment, but it was totally worth it.

Designer Kelly Giesen designed an absolutely beautiful studio apartment in NYC. Check it
out at her blog (kelly g-design) for inspiration. A bed can look beautiful with curtains in the
correct environment.

I love the sliding door idea that another commenter mentioned.
a couple of other ideas:
-old windows hung from the ceiling to make a "room" (like lisa bonet's loft in High Fidelity) http://www.apartmenttherapy.com/inspiration-old-95003
-get a modern four poster bed (like this one from room and board http://www.roomandboard.com/rnb/product/detail.do?productGroup=24505&catalog=filter&menuCatalog=room&menuCategory=191&menuSubcategory=135), and hang sheer fabric panels from it to create a private sleeping nook.

You can buy 4x8-foot sheets of coroplast (that plastic corrugated cardboard material) and use them as lightweight walls by either hanging them or attaching them to a more rigid structure.