Need help with your walls, look no further! Please take a look at these ideas.

http://www.houzz.com/projects/1520302/wall-art

It would be a good place to put something colorful, a suggestion is a hanging and framed world (or other) map. below are some examples!

As mentioned above by suzyq, some shallow shelves would work nice with the windows. You can line up the top shelf with the window sills, or just below, to let light in and incorporate them into the design.

For an adventurous take, use the windows as eyes in a (robot?) face design:

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Hi---

Great space!

I really like the suggestion made by suzyq. Good Luck!

I added a canvas to your pic so you can see what a long thin one looks like. I think that canvas would be at least 5' long and not sure how I feel about the distribution on the wall..it looks a little like a smile face :). But I do think maybe 3 square ones would work. They would be smaller and I would center it on your space and under the windows. I did yellow and an orange color so you can see the difference. If you are looking for abstract art feel free to check out my profile.

Also for my two cents I put shelves where people are not standing and bumping against :)

Do 3 similar framed pictures, no shelves please. Dust magnets and they are in the way for sitting and standing at table.

Here's a suggestion for your wall you might like .......for more artwork check my shop too...

https://www.etsy.com/shop/PooArtGallery?ref=profile_shopname

:))

Depth less than 3"

I would find a wonderful wallpaper, either something with texture or with an interesting motif - will transform the room.

Perhaps a vintage metal sign?