We have many ways to do this, depends on the requirement you can select one
1. Change users wallpaper through GPO
2. Change manually on per computer through registry
3. Change manually on per computer through changing the wallpaper1.bmp
1. Change users wallpaper through GPO
In active directory, you can change wallpaper through group policy, depends on the requirement you can configure this policy for particular OU so that it will apply all the users in the OU
If you want to apply to all the users in the domain, then you can use the default domain policy, which is linked to all the users, if you apply this group policy, all wallpapers will be changed
User configuration > administrative templates > desktop > active desktop > active desktop wallpaper.
2. Change manually on per computer through registry
If you want to change manually on per computer, use the remote registry, to edit the registry of a remote computer
Registry location
HKEY_CURRENT_USERControl PanelDesktop
look for convertedwallpaper and originalwallpaper
3. Change manually on per computer through changing the wallpaper1.bmp
Rename the bmp file to wallpaper1.bmp and replace to C:Documents and SettingsUsernameLocal SettingsApplication DataMicrosoftwallpaper1.bmp
Restart the workstation, it will be apply while the user next logon
