Help! When I try to set a skydome(in gnome)the background is just white. I've made sure that it is the right size and everything. It Just won't work

You said you made sure its the right size. What is the size, in pixels, of the picture you are using?

4096x1024

I've never been able to get an image to work correctly unless it had the same demensions for both width and height. What happens if you try a file that's 1024x1024, or 2048x2048?

I believe that some image types don't work either. I haven't used the skydome in awhile, but it seems like I had to use .jpg files (and maybe .png), and that .gifs wouldn't work.

Thank You!

You're welcome.

Here you can find lot of 4096 skydomes
http://skydomes.blogspot.com/

Yes, there is a problem with texture size. So the size or the fact that they are a power of 2 might help.
Look at glxinfo -l and look at texture size.
Sometimes lowering your image to this size will help. Sometimes, when beryl tries to use multiple texture (like 2x your texture size) it fails.
If rectangle texture is not present in glxinfo (depends on the card) then they have to be a square (awfull unless you have a square monitor.. rare)
If an other extension is not present (depends on the card) then it has to be a power of 2.

I have a skydome image that is a .jpg and it is 1920x1440.NVidia GeForce 7300GS card.