For your natural light, it could be worth getting a couple of small mirrors and placing outside. Position them so they reflect more light into the room for you. This will mean you can get lower light bulbs too.
Inside the room, you need to offset the blue with some bright posters and/or pictures.
Ditch the carpet and get a couple of thick rugs on the "hotspots" of your room that you're usually around. This will muffle the creaking too
You can get stencils and transfers to put onto that white furniture. The graffiti look or the tech look would be cool. But don't forget that you can paint wood to any colour you like.
For the bed, you could trade it for a new one with a friend. Or check your local freecycle for anyone ditching a bigger bed. Just ditch the mattress for a new one if it's "well used"
You'd be surprised at what you can pick up in room mirrors, trinkets and furniture in your local freecycle.
For your lighting issue, I would suggest switching out your bulbs to soft-whites. Amazing difference. If your current lighting is fluorescent, turn them off and get some lamps to put around your room instead. You can get a decent-looking lamp at Wal-Mart for as little as $10, and floor lamps there start at around $20. And I would surely try Johnathan's suggestion about placing a couple of mirrors near the window to reflect more natural light inside. Decent paint can be had for about $30 per gallon. Get a lighter color--if you like blue, go for a lighter shade on the same color card from which you chose your current color. Or try a very light gray. Lighter walls will make a great deal of difference in eliminating that closed-in feeling. You can get 5 x 7 area rugs in the neighborhood of about $50, to put in the creakiest places. If you go the area rug route, look for something that doesn't have a whole lot of dark colors, and try to incorporate some of your room's colors (floor, walls, accents) into it so you don't have too much going on, and everything fighting with each other. For the furniture, get some more paint, and paint it. Look for something that looks nice with your new wall color, and balance it with the rug(s). We are talking here about an investment of about $200 ( three lamps, a gallon and a half of paint, some sandpaper, and a couple of area rugs). If you don't have this kind of cash on hand, pick the most annoying thing about your room and fix that first, then the next thing, and so on, as money becomes available. As far as sleeping in a twin bed, unless you are extremely tall, perhaps you should just accept it and live with it, and put a full-sized bed on your list of things to fix. My hope is that you will pay for and do these things yourself--your parents have already invested a bundle in making that room as it is, and it isn't their fault that it hasn't turned out to be what you had hoped. Nor is it yours--some things just don't always work out the way we think they will. However, it appears that you are sort of stuck with what you have, and so the next best thing is to do what you can to make it more comfortable, yourself (with your parents' permission, of course). Good luck to you.
Paint the walls a girly pink. You might as well really hate it. Or go with a sky blue...2 coats...a day between coats. Floors creak and it is placed on concrete or on wood frame that is above the concrete? That is the only way the floor can move. Lighting is what you got. I used my room for sleeping in and that is about it. The walls were always black as it was night and the lights were not on.
I wouldn't be concerned as you are. When I was your age I was only in my room when it was time to do homework or go to bed.
I slept in a twin bed until I got married at 23. I didn't have any problems with it.
Adding a carpet that is big, comfortable and bright I think will really help fix up your place. Check out FeltBallRug.com (http://www.feltballrug.com). They have a whole selection of beautiful, hand-made rugs of all different colors. And their rugs are made out of wool so they are extremely soft and perfect to walk on!
As the old saying goes, "Be careful what you ask for. You might get it". Sounds like you did.
I had a room upstairs that I loved. When my parents asked if I wanted to move downstairs, I was ecstatic because of how much more space I would get. When all the renovations were done and I moved into it, as the months went on I began to hate my room more and more. First off, it kind of feels like a jail cell, because the only window I have is tiny and at the top of the wall in the middle of it, no natural light gets in because my room is underground except for the bit of window. Second, because of that, I regret my colour choice because it makes the room feel darker than it already is (it's dark blue). Third, I wanted to keep the carpeted floor, but my parents went and got hardwood for it. The room is so big that my carpet doesn't even begin to cover it, plus the floors creak. The lighting in my room is too unnatural, it is so bright and annoying, and there can be no in between balance between the natural light and the light I have in my room. And finally my furniture. It is kinda girly and white (I'm a guy), and I am 16 years old with a twin bed that I've had since I was 5. It's way too small. My mom gets really angry when I ask her for at least a new bed because I really need one. I don't know what to do.