How to redesign my room? ?

I want to change my room up, but I'm can't get new furniture and stuff.. But I CAN paint! (: right now I have all white furniture.. With a built in white desk. -_- A window bench (That has a built in like Orange/ Yellow pillow? :| )and a double bed that has a black iron Head/Foot board.. my covers are the blue/green/Purple ones from Ikea in the big squares, and I kind of have rainbow pillows? :( How could I redesign it to make it look older and more mature? thanks! (: Also, what colours should I paint?