Depends on what you are looking to do specifically. There are some DIY home improvement sites that can help, such as HouseLogic.
Yukia and DIY
DIY Nation - 2011 Dream Bedroom 1-7 was released on: USA: 8 October 2011
If you are good with do it yourself projects, you could install a bench in your bedroom window. My advice would be to visit a local DIY store in your area. They are generally quite good at providing advice for your DIY projects.
use your imagination find horse posters cut them out and make a collage or maybe make a mural for your wall . There are lots of ideas maybe try some of mine or some others.
hollister.
posters
Stuff Happens Hosted by Bill Nye - 2008 Bedroom was released on: USA: 30 September 2008
get nice boxes fill them with your stuff and stack them up
You can get bedroom lighting ideas from decorating shows on DIY network. You can also get them from places like Lowes and Home Depot. Another place you can find these kinds of ideas are online at the HGTV website.
The bedding is from zgallerie
you can put up a funky colour, by a teenage bed (argos) and put all your nice stuff on display
well.... it means that they're going to have some "fun in the bedroom" like kissing and all that smooching and gooching... 'n' stuff...