Bedroom ideas: teenage girl?

Im a teenage girl, and i need to decorate my room. I'm thinking maybe lilac walls, and a couple of twilight posters (or any movies i like). I know that people say that there's no point in painting your bedroom if you are going to put posters on, but it does matter. It can give it a different feel (e.g. hot pink gives another feel to whitey cream). If you have any opinions on this, please reply. I don't have to have lilac, maybe light blue, but i need something pale. Thanks all for answers!