Options configurable through GNOME Lock Dialog Preferences include:

 * Changing the lock dialog theme
 * Enabling automatic screen locking, and setting the delay after the screensaver activates before locking.
 * Enabling user switching from the lock dialog.
 * Enabling logging out from the lock dialog, and setting a delay before the option is displayed.

The whole project is hosted on Launchpad, so contact the project leader here if you want to help out.
Translators are especially needed right now.