If you have any pretty dishes you could display, especially bigger serving pieces, that would be an obvious thing that would fill up a ton of that space. Or you could just make them bookshelves and fill them with other books as well as the cookbooks you have there.

You could always turn the cookbooks on their sides as well....still looks good and easier to read the title :-)

How about collection of pretty bowls like lion's head soup bowls, white small cake plates or white ceramic or enamel tea pots. All these are ready available and cheap to purchase.

And by turning them on their sides, I mean laying them flat so that they will fit height-wise

I used to live in a four-plex with very similar built-ins. I used mine for what you'd expect -- knick knacks, cute books, boxes, etc -- but my neighbors used theirs as storage for their antique cocktail class collection. Granted, not everyone has one of those (!), but I'm sure you could easily find some champagne saucers (like these: http://www.etsy.com/listing/94204868/vintage-fostoria-melrose-etch-no-268) and tumblers (like these: http://www.anthropologie.com/anthro/product/home-tabletop-glassware/973172.jsp) at a good resale shop.

how about photos of your loved ones mixed in with things you may collect? or some food-oriented things (antique utensils, framed recipes that you enjoy, kitchen-y art/signs ("eat"), etc) to go with your cookbooks? a small plant or two, perhaps potted in an old cooking pot? (also, there's lots of information on apartment therapy and other sites about ways to arrange stuff on shelves ... "pyramid" design and all that).

basically, i suggest putting on those shelves whatever makes you smile. and enjoy those built-ins; they are lovely!

kathy

Put your possessions on the shelves. If your possessions won't all fit, pick the most beautiful ones and store the others.

If you have put all your possessions on the shelves and some are still empty, you might want to acquire more possessions. The only rational way to acquire more possessions is to ask strangers what you should buy. Strangers who work in stores will be especially glad to tell you what you should like, but random people from the internet are also good at it.

Seriously, if you don't fill them up with majolica/Jadeite/Hummels/chickens/fiestaware you're doing it wrong.

You could always store stuff, if you need more storage for unattractive things, in baskets or other nice containers, on the shelves.

I second the dishes idea - If it were my space I'd put a coffee service set there with some cool mugs (upside-down to avoid dusty beverages), my french press, and other stuff I use often but not every day.
You could also utilize it for bulk foods if you find yourself lacking pantry space. Find some food grade glass jars (I use a mix old Planter's Peanut jars and spaghetti sauce jars with painted lids) and use those to store sugar, beans, rice, pasta, etc.

Haha, @Bee for Brian, so true.

Put things that you enjoy there, don't you have any collections that you would like to display? Decorative items that make you happy? I can see the issue of the depth of the corner shelves being awkward, but anything narrow or smaller in size will work. Make it what you love to see, not what others tell you is the thing to do!

lol @Bee

You can keep an eye out at flea markets and thrift stores for fun vintage kitchen supplies - a fun cookie jar or something like that... but in the end put up things that make you happy.

Why not change the height of the shelves? (removing a few, if necessary)
Cut out the arch at the top, while you're at it. Tada, whole new look.

If you read AT enough, you'd know you don't need to keep furniture in its original form.

How about storing your spices there? Light isn't great for spices, but maybe in little amber glass jars or in stainless steel containers? Most people would kill to have some extra storage near their kitchen. Extra glassware, stored upside down to keep the dust out. Looks like when similar pieces are massed together. More uniform and less cluttery.

I'd spread out what you already have, to fill the shelves (divide cookbooks, some upright, some on their sides), sparse looks great when the shelving itself is beautiful and then I'd get some storage jars and fill them with smaller items like shells or kitchen items such as cookie cutters. Then take your time. Make it a rotating display of whatever interests you at the moment or in the season. Perhaps start a collection populated by thrift shops, garage sales and flea markets: pottery in a specific color or two (I collect white, pale aqua, pale yellow but only specific shapes), spelter figurines, leaf dishes, whatever interests you.

a bar! bottles below, glasswear above. use both bookshelves if you drink a lot.

LOL @BEE FOR BRIAN...

agree with @LGS.

"Strangers who work in stores will be especially glad to tell you what you should like" LOL @Bee for Brian

Figure out what era your apartment is from and then go to flea markets, Goodwill, Etsy, ebay etc and get items from that era. Or, photographs and/or ads and/or labels from that era in cute frames. I have an old wedgewood stove and found a 1950's full color full page magazine ad for the same stove on ebay for 10 dollars. With a cheap frame its a perfect (and easy) thing to put on the shelf. An old copper pot, mortar and pestle, milk carton, cookie jar, etc would be great too.

Don't forget to dust!

Go to the library and find books in the decorating section. You might see some on displaying collections, etc. Items with similar colors but different shapes and sizes often work well together.

Gosh.. If you really don't have any knickknacks to put there count yourself lucky. Stuff always seems to have a way of accumulating in life, so I personally would never go out any buy anything if its main purpose is to fill a space... if it gives you the excuse to get something you always wanted but didn't have space for that is another matter. Maybe you can just shop my house to see what might work well. If you are trying to keep it kitchen dining related, which you didn't mention, then items you use, but not often, as was suggested before is a great choice. Maybe things dining related that don't need to be accessed in the main kitchen that often such as silverware in a mason jars or other nice jar, napkins, trivets, etc would would well. Also board games, but you know, the pretty ones.

Really, Nicole? Really??

That made me laugh, too, because I accumulate so much junk the idea of empty shelves screaming to be filled with stuff seems hysterical to me.
This being said, here's an inexpensive suggestion for you: put some little planters with succulents on it. And keep some space open for a vase with flowers from time to time.

A platypus!

...or a plant works too. Art. Dirt collections. Seashells. Branches. A litter of pet rocks. Why not just divvy up the books already there, get one or two plants, spread the stuff out a bit and wait for it to fill up organically? Open shelf space ain't a crime. :P

Or a typewriter. If in doubt, get a typewriter.

(I'm not hating, I have three and a typewriter cart.)

these are cute as-is, with no need to hack them up (or do anything in the yonella post above). since they already are painted, consider painting the back walls another colour, creating a frame for objects inside. subtle: palest version of your wall colour. traditional: wedgewood blue or striped wallpaper (remnant). bold: red, yellow, acid green. can paint back when you move out & fake exact match to front panel.

p.s. forgot black (but things could get lost in the depth).

I'm not a big fan of open shelving, so I'd look to fill these with something "quiet," (and relevant to the room) like white dishes and clear glass, especially if these built-ins are positioned in a focal point location.

As far as your unhung art, replace the chalkboard with it.

I would paint the interiors a soft pink. Then, cover the cookbooks in white kraft paper, and spread them through all the shelves, and add in some white and clear vases, then add single blooms in a few random vases.

What's with the unpleasant comments when someone just asks for help?

Here are some beautiful bookshelf inspirations .from our blog Pictures worth a thousand words:)

I would remove the shelves (if possible) and insert some interesting wine racks. Or even if the shelves are adjustible you could change the height and save some pretty vases and wine bottles for display.
They're easier to dust than trinkets and plates. =]

That's the spot for your soup tureen and other serving specialty dishes!

We have a weird shelf in the kitchen at my house - while waiting to save up to redo the kitchen, we're using it for mason jars and old sauce jars filled with dry goods like lentils, pecans and oatmeal. Looks nice, keeps the dry goods at hand.