Specify desktop wallpaper image via GPO results in blank background

@Simon-catlin has good hints, and here's a larger list of things to check:

Note if you have to test this via RDP, ensure the RDP session is set to max fidelity (the desktop background is checked or you'll never see it).

  1. When having a GPO issue, you need to only troubleshoot that issue. Just in the screenshots you have dozens set, but you first need to just test one: setting the background. Move the computer to a OU outside of all other GPO's and create a test GPO to walk though this, which will help you find what the hangup is: permissions, conflicting GPO's, etc.
  2. Once you've verified you can set the bmp to a local default file built into XP, then manually copy the one you want over, and try setting it.
  3. Once that works, then test the GPP. Note that you'll need to use the file copy in the Computer GPP so it copies before the user logs in.

Lastly, it may take multiple user logins to see it. With some GPO's, especially in XP, they are set on first login, but don't take affect till 2nd login. Often you'll see info about that in event logs.