How can I get the Android to use wallpapers sized to my screen resolution? When I only have one "desktop" on my Android phone and I select one of my photos for the wallpaper, it asks me to crop the image.  The cropping tool only allows an aspect ratio that has nothing to do with the real aspect ration of my phones screen resolution. Why?

I have a Samsung GT i5800 running Android 2.1update1.
If I remember correctly, the aspect ratio is always for a 5 desktop scroll. If you have enabled only one desktop, the you'll see just the middle part of the wallpaper.