How can I decorate a small room that has black walls.?

My brother recently moved out so I get both our rooms. my mom doesn't want me to repaint. Even though I can paint the ceiling since it's black as well. The room is only like 10 by 12 very small. I want it famine and sophisticated, and maybe brighten it up a little. I was thinking maybe doing it up with white and purple? Any ideas? If it helps I'm 21.