I am going to take the easy way out on this. Take a look here:
http://www.zztechs.com/en/zlauncher.php
Down at the bottom of the page is the user manual. It is very well written and concise.
I have ZLauncher setup on both my 650 and 700p with wallpaper/background images that are jpgs and the function works very well.
Copy the jpg file to the SD card - /PALM/Programs/ZLauncher/BackImage
From Theme Manager, select "Back Image" then select the jpeg file, then the tab you want it to be associated with. It then compresses the file and copies it to device memory.
The tabs I have active are: Unfiled (I set every application to Unfiled as a default action on my part); PlugIn; All (shows everything), Main (nothing there - a red screen for night time use); Multimedia - nothing there; Card (very plain); and Invisible for those I do not want to show up in the "Unfiled" tab.
You can have as many backgrounds as you have tabs. You will need jpegLib in main memory.
I have not deleted the Multimedia or Main categories - no reason to or not to.
Ben
Ben