Well you could go bold and bright and have lots of fun colors in your room. Lie this

http://static.howstuffworks.com/gif/teen-bedroom-decorating-ideas-2.jpg

or I like here how they painted the squares on the walls:

http://www.actioninterior.com/images/services/childrens-and-teen-rooms/children_squares_on_wall.jpg

Or you could go with calmer more relaxing colors like here / / See how they added pops of blue and green.

http://www.actioninterior.com/images/services/childrens-and-teen-rooms/children_green_and_white_bedding.jpg

Here you come try the circles on your wall but of course you can paint them any color YOU want and if you don't like it remember it only paint.

http://www.actioninterior.com/images/services/childrens-and-teen-rooms/children_white_and_circles.jpg