There are three inexpensive things you can add to your room to make it more bright and cozy.

Curtains: You can buy a great set of bright curtains for under $15. A room without curtains just looks bare. Be sure to choose a bright color that you love or a bold pattern.

New throw pillows and a cuddly blanket on your bed: Even if you have plain bedding, a new blanket and throw pillows will liven up your bed. Cuddly blankets also add a touch of luxury.

An area rug: Adding a rug to your floor will warm up the space and make it more cozy. If you find a rug like this zebra area rug and you have hot pink on your bed and curtains, your entire room suddenly has a theme.

Even with white walls and brown furniture, you can definitely liven up the space with a few small touches.

I don't know how to decorate my room?

If you are worried about adding color, you can do one wall up with color and leave the rest white. For something a little less permanent that paint, try one wall of wallpaper. Wallpaper is huge right now, and doing one wall won't overwhelm you entire room. Find a bold pattern with purple touches if you can.

If you have white walls, you can focus on your accessories to liven things up. Make a corner of your room into a hangout by adding bean bag chairs, a magazine rack, a place for your iPod, and pillows to relax on. You may want to add a large shag area rug to your floor for a comfy touch.  An area rug like this Plush Element Shag area rug would be comfy and cushy to sit on.

Add accessories to your walls to take up blank space. Mirrors are a great addition to make a room look larger and add some life. Photos of your friends and family look great in picture frames, or you can buy the re-stickable wall decals that look like frames. 

New york style bedroom?

You can buy large murals that will take up an entire wall and turn your room into a city scape. Alternately, you could go with a modern feel and focus on one feature wall that would be grey with the rest cream/white.

There are so many touches you could add that would make your room have a New York feel. You can buy gas light replicas from a place like Pottery Barn or Restoration Hardware. A great light in the center of your room really brings the space together. On your floor, add a large, modern area rug like this Geometric Grey and Black Area Rug.