In the June 2011 issue of Better Homes & Gardens, a home owner used grasscloth attached with adhesive transfer tape to the interior back of a bookcase. That gives color and texture and perks up the bookshelves. We only painted--a sort of pale terra cotta--the back of our living room built-in bookshelves. They had been all white. They look so much better now!
I saw an Olympic pink paint color in the issue that I really like: Bunny's Nose.
For a fantastic centerpiece or accent, plant succulents in a really big shell.
Another good idea from that issue is adding two levels of Shaker-type pegboards. Our house is full of pegboards; they're useful and can add a colorful accent, but I never thought of putting them at a lower level for children.
Oh, in a recent mail advertisement for Martha Stewart Living, they used a flower stamp (or you could use a stencil) and ran it as a garland over the headboard, the wall, and a lampshade on the bedside table. That is a fun idea!