Why don't you do one wall blue? One of the little girls I sit for has 3 of her walls painted a cream color, and one wall painted a violet color. It gives color to the room w/o it being overwhelming. I've seen several rooms done like this and it always looks good.
Have you thought about maybe putting one of those wallmurals up? Another family I work for has a parrot one in the little girls room and it looks cool.
Here is a raceway one-
WALLIES Race Car wallpaper wall mural
HEre are some Jungle ones-
Colorful 3D Safari Wall Mural for Decorating Kids' Rooms Jungle Animals Wall Mural for Decorating Kids' Rooms 3D Safari 2 Wall Mural for Decorating Kids' Rooms Jungle Wall Mural for Decorating Kids' Rooms
I want to see pictures after you finish his rooms!