1) Measure and cut mirrors to place against the back of the built-in. If they are cut accurately, you won't need firm glue to hold them in place. Like the mirrored bedside table, this is an affordable and non-permanent project. When you move out, you can take your mirrors with you.
2) Add scraps of wallpaper or fabric to the back of the bookshelf, like Viv of ish and chi pictured above.
3) Paint the back of the unit an accent color or even use chalkboard paint. You'll most likely end up placing objects in front of the paint but if not, you have a fun place to write sweet notes or draw pictures for your family and friends.
4) Keep the entire unit it bright white. Like the photo pictured in the beginning of the post, leave your built-in as is and use home decor to make it your design style.
Have you made over a built-in unit? Tell us your design idea below and upload some photos in the Apartment Therapy Flickr pool.
Check out more shelving ideas from Apartment Therapy:
(Image via Rene's Bright & Sunny Home)