This is how you update a user’s wallpaper scriptomatically.
xcopy /y \\TheComputerName\WallPaper\new_wallpaper.bmp “%userprofile%\”
REG ADD “HKCU\Control Panel\Desktop” /V Wallpaper /T REG_SZ /F /D “%userprofile%\newa_wallpaper.bmp”
REG ADD “HKCU\Control Panel\Desktop” /V WallpaperStyle /T REG_SZ /F /D 2
REG ADD “HKCU\Control Panel\Desktop” /V TileWallpaper /T REG_SZ /F /D 0
%SystemRoot%\System32\RUNDLL32.EXE user32.dll, UpdatePerUserSystemParameters