Something original like a stop sign or a giant origami some thing original modern artwork or a cool mural plasma ball christmas lights stero retro stuff guitar( or any instuments ) also they have good ideas on the DIY network on tv
Depends on your likes and interests. If you love music and are more of a scene kid, posters are pretty common. If your a girly girl, maybe cute accessories and other decorations like throw pillows and stuffed animals. ( I know it sounds kiddish, but their actually pretty cute ^_^) If your an anime freak or video game nerd er something like myself, put posters of all your favorite series.
you can put in a tv,bubble chair,door beads,cute curtains,a lava lamp,mirrors,maby a cool lamp that you can find at a local home goods store,posters,bean bag chairs,small benches,you could put lots of stuffed animals,or get a really bright bed spread,black lights,christmas lights,small chandiliers,or even some cool lights you could probabally find some cool ones in home depot or a lighting store well i hope this helps
Its really all about trying to make your room look expanded, especially if you have a smaller room. Try mirrors, bright paint in the room for the illusion of it reflecting off each wall, moving your furniture around in different areas, more clothes in your closet and get a smaller dresser, and some cool ideas that make your room unique is no matter what the theme of your room is, you can add things such as Christmas lights, furniture made from store crates, paintings and posters, etc. This is a really cheap and easy way to have your room look different and is usually done quick.