You need to get a regsiry editor, something like
this.
Once you have installed it on your PPC run the application.
The you go through these folders
HKEY_CURRENT_USER\Software\A_C\Slide2Unlock
You will see a page full of values, if you dont press the right soft key to get the values.
You will see 2 String that say "Wallpaper"(The Wallpaper when your phone is in potrait mode) & "WallpaperLandscape" (Wallpaper when your phone is in landscape)
Change the Location of the current image to the location where the picture you want to put up is (example \Storage Card\My Pictures\example.jpg)
Restart iLock Run Slide and ur good 2 go