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