What are some good room ideas?

I'm 16 and i'm moving soon, and my mom gave me an 800 dollar budget to pick out brand new furniture. thats probably not alot for a room, but i NEED new furniture . like this is really bad, my bedroom set right now is decent but plain, not to mention i got bored one day nd fingerpainted all my furniture. so i need cool room themes! something GROWN UP like, NOT pink or frilly, and cool to show off :3 thnks!