I like this ruffle fabric lampshade idea for the girls' room, but am thinking it would make a great small shower curtain for their shower stall, as well.
To cover a lampshade, place a piece of wallpaper on a flat surface. Roll the shade along the wallpaper, tracing both edges. Add 1/2" to each edge, cut out the cover, use spray adhesive to attach it. Snip the excess paper at even intervals, fold to the back of the shade and secure with spray adhesive.