To change the GDM login background in Ubuntu Karmic Koala

I found to my utter consternation that one cannot change the login background in Ubuntu Karmic Koala (or Linux Mint 8, for that matter) from gdmsetup.

I found this solution after a bit of googling -

1. Firstly, we log out of the current session and return to the GDM login screen.
2. At this point, pressing Ctrl-Alt-F1 throws up the terminal.
3. Login to this terminal with your username and password.
4. Then issue the following command -
   $export DISPLAY=:0.0
5. followed by -
   $sudo -u gdm gnome-control-center.
6. At this point, pressing Alt-F7 brings us back to the GDM login screen with gnome-control-center
   
7. Selecting Appearance from gnome-control-center and making the appropriate changes to the background, font.
8. Closing the gnome-control-center window reveals the login screen with the new background.