It seems you are stuck in a 3 year old toddler's room at 11 years. You have not given me much info to work on, so I cannot give much specific advice.
But here is what I would say:
1. Make a list of all your interests - music (or Lady Gaga); sports, movies, dogs, tinkerbell etc. Is there anything you specifically want to show in your room - a theme?
2. Or you could choose a color scheme instead and put more than one interest in the room - like a bright room with reds and oranges or more sedate with pastel pinks or sky blues. Then add wall art such as a photo of your dog (or of you playing the guitar) and color the frame in the room's color schemes.
[Find a bed-in-a-bag set or comforter that you like and match the rest of the room to its colors.]
3. Also make a list of all the activities you plan to do in the room - sleep, study, sleepovers etc and create different zones in your room. If your room is too small - add different rugs to differentiate the zones.
There are a lot of ideas. I would suggest you go through the pages on this site - you will find ideas that appeal to you. Write them down and cut and refine to your taste.
Hope this helps. If you need any further ideas/help, write back here in the comments section and I will be glad to answer.
