I understand it can be hard to decorate a small room, and finding a theme can be a challenge.
In a small room sometimes "less" is more. I would not put to much decor in the room and make it feel "over-done".
As far as a room theme goes, look through some of our suggestion on out girls room theme ideas pages.
A great way to get started with a room theme is to utilize the stuff you already have. (This can also help you save some money! :)
Do you collect anything?
Do you have a favorite hobby?
Like a certian color?
All of these could help you decide what theme to use?
I would love to see your room, and what you are working with. Feel free to send me a picture, and I will see if I can help you create a bedroom design that you would really love!!