With a typical installation of Windows (regardless of what version is installed), the Windows Explorer background is white. HOW BORING!!! With a little experimentation with Skinstudio 6, I found out that you could use any Bitmap or PNG file to fill your Windows Explorer background. Don't believe me? Click on the link at the bottom of the article, then you will believe me.
I also skinned the left & top navigation bars and filled it with seperate images.
To effectively fill the entire explorer background without tiling, use an image that's at least the size of your screen (i.e. if you use 1280x1024, use a 1280x1024 sized image, etc.[preferably a light-colored wallpaper]). Just make sure that you can still read the links to your folders and files, or this will just get in the way.
This works well for both Windows XP & Vista.
Enjoy!!!