How to decorate my room to fit my style?

I am a 15 year old girl. I love rock music, and the "rock scene" i guess you could say, but also the beach scene. I'm moving my room upstairs to the bonus room so i'm needing new ideas. i'm not sure what color to do the walls, and what color bedding i want. i've been looking at beach theme rooms, and gothic styled medieval type rooms, but i'm not sure. i dont exactly want a "theme" to my room i guess, i just need colors to go off of. i want colors that'll go with my band posters hanging on my wall, to my seashell windchime hanging from the ceiling. weird combonation i know, but i need help.