We keep toys under the stairs. It gets messed up fast -not a big space and too many toys. At Kara's Korner she put up the cutest book shelves for her daughter's nursery. Check out the tutorial and pictures HERE.
We made our own and then modified it just a bit. By modified I mean - we hung one upside down. We didn't plan it at first but then we realized we needed a wider shelf for stuffed animals. The girls also keep their Liv doll wigs up there away from their brothers.