GDM3Setup, a tool to tweak the GDM3 login screen / lock screen, has been updated recently to support the latest stable GDM 3.6.
- Change the GDM3 GNOME Shell / GTK theme
- Change icon theme, wallpaper, cursor theme
- Enable/disable automatic login
- GNOME Shell: change logo, show date in clock, show seconds in clock
- GTK: change font, disable user list, disable restart buttons
In my test, some GNOME Shell themes didn't work properly with GDM and caused it not to start, so I suggest you don't change the GDM GNOME Shell theme! Also, an user has reported that the automatic login feature causes issues too. Only use these features if you know how to restore everything to default without a working login screen.
GDM3Setup is available for Ubuntu, Debian, openSUS, Fedora and Arch Linux and can be downloaded from GitHub:
Note: even though the GDM3Setup page says the Ubuntu deb package is for Ubuntu Oneiric Ocelot, it works with Ubuntu 12.10 Quantal Quetzal and the latest GDM 3.6.
How to change the GDM 3.6 background image
GDM3Setup supports changing the GDM 3.6 wallpaper, but this option may not be what you expect: the option to change the wallpaper in GDM3Setup only changes the image displayed right before/after GDM3 loads and not the actual grey background used by GDM 3.6 for the login / lock screen.
Until GDM3Setup gets an option for this, you can manually change the GDM 3.6 grey background image. The image used by default is located under /usr/share/gnome-shell/theme/ and is called noise-texture.png.
Like its name says, the grey image used by GDM 3.6 is a pattern, but you don't have to use a pattern and a regular wallpaper image works too. To change it, open Nautilus as root:
gksu "nautilus --no-desktop /usr/share/gnome-shell/theme/"
then make a backup of the original "noise-texture.png" image and replace it with the image you want to use as a background for the GDM 3.6 login / lock screen.