Here are a couple of 9/11 PC Desktop Wallpaper images I made.
They are both 1024x768 and about 100Kb.

http://img264.imageshack.us/img264/7017/911truthnowbm3.jpg

http://img440.imageshack.us/img440/214/911wasaninsidejob1hi0.jpg

If you want them different sizes, I suggest freeware IrfanView for simple image manipulation.

http://www.irfanview.com/