I know this is an old tread, and Windows 7 is an OS fast becoming obsolete. But for the occasional user: I have dealt with this for years in my shop. I am close enough to IT to have certain privileges on my laptop, but not close enough to stop then making stupid GPOs which - of course - affects me as well.
On XP I am certain, on Windows 7 this is just an inspiration: This kind of changes to Registry will not take effect until you reboot the system! And since you try to circumvent a GPO, this equals "mission impossible" in many situations. There are, however, a way to force an update of the Registry to be applied without rebooting...
The thing is: You don't need to reboot - you need to flush the cashe of registry settings - which is a part of a reboot.
Solution (on XP at least):
call :quiet>nul 2>&1
:: Configure Wallpaper (command prompt method works only with bmp files)
REG ADD "HKEY_CURRENT_USER\Control Panel\Desktop" /V Wallpaper /T REG_SZ /F /D "C:\WINDOWS\Web\Wallpaper1.bmp"
REG ADD "HKCU\Control Panel\Desktop" /V WallpaperStyle /T REG_SZ /F /D 0
REG ADD "HKCU\Control Panel\Desktop" /V TileWallpaper /T REG_SZ /F /D 1
:: Make the changes effective immediately (only XP-compatible)
This works (worked) well for me on my XP machine, the trick being the last line: Execute "user32.dll,UpdatePerUserSystemParameters" as part of the bat-file. This takes the place of a "reboot". :-)
I put this in the Start folder, and added a shortcut key combination to the bat file: This way, my pc started with my own wallpaper, and when the GPO refreshes a couple of times during the day, I hit the shortcut key, and get my preferred view back (Which is infinitely prettier than the "black screen of depression" which is company stock) ;-)
I haven't got around to fix this on my new laptop (running Win 7) yet, but I guess someone out there can get inspired by this (XP) behavior and research further.