you could pick colors ( maybe 2)that you like the most that will complement each other and work in with what ever else you have in your room that you are going to keep; add in just your favorite things and clean out all the rest to give you more room and a neat new look, can you afford new curtain's or drapes in your room? If so that might really help with the look.

Knowing your age and gender would help. Also, what are your favorite colors?

as you like it subject to cost restrictions and practicalities

any further info you want to supply

your age

size of room

what you are/can change

interests

EDIT

maybe post the Q again with a shot of your room

include some ideas youre having right now

who is paying for it

who is doing the work

what you are changing .. for instance, is it to be painted, are you swapping furniture, new curtains and so on