What about paint the top half of the wall gray and then do purple and lavender stripes on the bottom half. Perhaps separate with a chair rail.
Are you using a light gray? Be careful with the gray you use, you don't want it to dreary looking. KWIM
Are you doing stripes? I have a 3 color striped wall in my sons room, pictures are in bio. The ther 3 walls are white, with just one of the stripes continued around the room.
I have a couple pics in my bio.
if you want something really simple, i'd say something like this or the one above my post, but maybe leave the top white, the horizontal stripe gray, and the vertical stripes the 2 purples.