How to make my room look more like a teen room?

okay, so i just painted my room a pastel pink but now it looks alot more like a kiddies bedroom so i need to make it seem more my age (15)... i've got a few tester pots of paint (dark pink, light and dark blue) so i can put designs up, but dont know what to? also because its newly painted i cant put up posters just yet and i'm on a low budget... Please help :)