Bedroom help?

Question:I'm pretty much broke. I want to decorate my bedroom and make it a place I actually enjoy being. Here's what I'm working with, and keep in mind I rent so I cannot do anything perm. (painting, shelving, etc)
Floor is blue carpet (dusty darkish blue) and walls are light grey panneling and white. I have one tallish window, A dark wood bed and a closet with two sliding doors-it's brightish wood. Color scheme, theme ideas, pictures, do-it-yourself ideas, links etc would be greatly appreciated and make a "best answer" more likely.

Oh, and a big problem: I have this wall a/c unit and it's brown and awful and big. Any creative ideas to cover it up and yet keep it functional without doing anything permanent would be awesome.

Answers:
being broke sucks but there are SOOOOO many solutions out there for you! Ok, I am just going to throw a whole bunch of ideas out at you...

My first Idea is for a general color scheme. Since your room is light grey, white, blue, dark brown, bright wood etc I would say do something with some reds, bold purples and blues.(and green if you are a green fan, I don't really like pairing green with blue unless it is light green with blue, its just one of my personal weird things. But if you like green, add that to the mix!)

1) Curtains: Measure how tall your window is down to the bottom. Go to your local fabric store or Walmart. Look through their solid colors for the colors I listed above. Get enough fabric to double it up to cover your window. A single layer is usually too thin and doubling it up will make it a bit thicker and will block the light at night. I would suggest looking for fabric that is a bit thicker in general...i am not sure how else to describe it though! At home, fold the fabric in half long ways and sew a seam 2" from the top fold. This is where the curtain rod will go. Alternatively you can staple it. Then hang your curtain! If you don't have a curtain rod, try getting some small finishing nails at a hardware store (or Walmart) and tack the curtain up. To tie the curtain back during the day, you can do a couple things. First, you can get a bandana or some other piece of fabric and just tie it in the middle. Or you can put in a longerish nail or a hook with a sticky back and cut holes in the two ends of the bandana or fabric and then tie the curtain to the side using the hook/nail and the holes in the bandana. If you window is too wide, you can use two fabic panels and then tie them to opposite sides.

2. For that big ugly AC wall unit...get some more fabric in a different color and wrap it around the unit. It needs to be long enough so that you can tied a know/bow at the bottom so it will stay. Then you can decorate it with picture frames or put some books on the small ledge that it creates!

3. Wall Decorations. Hit up your local thrift store! Sometimes you can fine interesting and neat art pieces! I also like shopping at Ross and Marshalls and they have some good stuff too, but it will cost a bit more. I would suggest getting some mirrors on the walls (large or small) because they will reflect light into the room to make it brighter. Then there is always the Do It yourself solution: Go to Walmart's art section and pick up some cheap acrylic paint and some canvases. Last time I was there you could get a 4oz bottle for 42 cents and a pack of 3 8x11 cardboard canvases for cheap also. Then paid the canvases in red, blue, purple. They can be solid colors or you can mix them up. Then hang them on the wall with finishing nails or sticky hooks either in a row or in a square, triangle etc. or if you or one of your friends is an artist, paint or draw something and decorate that way!
Something I always like doing, is getting some black frames (Walmart, IKEA, Ross etc) and putting black and white photos of friends, home, places I have visited in them. Black will match alright with the rest of the furniture and carpet and will look good against the light grey/white walls. Also it will stand out amongst the blues, reds and purples that you are decorating with.

4) Other random ideas
Whether you like some of this stuff has to do completely with your personality...but I thought I would throw it in to give you options.
My friend did a room where she pinned up (with thumb tacks) to shawls. One was larger than the other, but had them angled so they just barely criss crossed at one end of one of the shawls. You could try something like this if you have a big empty wall.
If you love shoes, pin your shoes up on the wall! You can use thumb tacks to go on either side of the heel to hold it up. To make this work, they will need to be pointing down, but you can still put up lots of random shoes and get friends and family to donate more. Its kind-of retro unique look, but it will definitely draw comments! Make sure you have a variety of color up there too!
Grab some tulle from Walmart (about 7 bucks for a 60 yard roll thats 6" wide), double it up so it has some substance to it and run it around the top of your room where the walls meet the ceiling pinning it up every now an again so it has nice graceful curves to it.
There is always the option to make a collage of photos on the wall too! A neat idea for this would be to put up construction paperin strips in the color of your choosing so it makes a rectangle on the wall. I would personally cut the strips so they are 3-4" thick and make the "frame" with them. They can be stuck to the wall with poster puddy and so can all your photos!
If you have lots of postcards, put them up at the top of your wall so they act kind of like a boarder. This can be really fun if you don't have a particular color scheme (or don't really care if it matches said color scheme) and your style is eclectic.

5) Finishing touch...have a plant somewhere...this you will probably have to buy. I suggest a bamboo plant because they are smaller and you don't have to water them every day, and they don't require lots of sunlight, so they do well indoors.

I think thats about all I have for you. I hope i sparked some ideas in your head!
Have fun and good luck!