Last week we've posted about changing the GNOME 3 login screen background / GTK3 theme via command line but if you want to use a GUI for this, you'll be glad to know that one already exists: GDM3Setup.
GDM3Setup is a simple GUI tool to tweak GDM3 (GNOME3 login screen). Using it, you can change the following GDM3 settings: wallpaper, GTK3 theme, icon theme, logo, disable the login screen user list or restart buttons.
GDM3Setup is already available in AUR for ArchLinux users. As for Fedora 15, a small tweak is required to get it to work (see below).
In my test, GDM3Setup didn't work in Ubuntu, but it doesn't really matter anyway because Ubuntu 11.10 Oneiric Ocelot will use LightDM instead of GDM by default.
Get GDM3Setup to work in Fedora
1. Firstly, install "git-core" and then get GDM3Setup using the command below:
cd git clone https://github.com/Nano77/gdm3setup.git
2. To get GDM3Setup to work on Fedora, you must install "beesu" (a gksu alternative for Fedora) and replace "gksu" with "beesu" in the gdm3setup.py file. The commands below will take care of all this automatically:
sudo yum install beesu sed -i 's/gksu/beesu/g' ~/gdm3setup/gdm3setup.py
3. Now you can launch GDM3Setup in Fedora by going to the "gdm3setup" folder in your home directory and then doublickinging the "gdm3setup.py" file. You can also install it if you want, by using the commands below (after this, you'll be able to launch GDM3Setup from the menu):
sudo install -D ~/gdm3setup/gdm3setup.desktop /usr/share/applications/gdm3setup.desktop sudo install --mode=755 -D ~/gdm3setup/gdm3setup.py /usr/bin/gdm3setup.py sudo cp -r ~/gdm3setup/locale/ /usr/share/locale/
If you want to use "su -" instead of sudo, make sure you enter the exact path to where you've downloaded GDM3Setup (e.g.: /home/YOUR_USERNAME/gdm3setup).
Once you run GDM3Setup, click the "Load" button to load your default settings, then change the wallpaper, theme or any GDM3 option you want and click "Apply".
Important: to be able to change the GDM3 login screen wallpaper, the image must be copied to /usr/share/backgrounds/ and the themes under /usr/share/themes/.