Tips on creating a modern room?

My sister has been out of the house for awhile visiting every now and then. She has a much bigger room than I do and so my parents were thinking of switching our rooms. The only problem is that I have a very childish room. There are some good things in my room, but I wan to make it my "style". Any ideas from the following interests that I have: Poetry, I'm a devout christian, love nature, theatre, books, people, video games, writing in general, animals, the ocean, etc. Ideas? Also, I need ideas for the color to paint it. My favorite color is red, i like blue green and orange though. Also, any cool gadgets to name of? I want my room to be modern and more mature, but "me" as well. Thank you!