Fedora 18 comes packaged with the Gnome Display Manager – GDM as it’s default login manager. There isn’t a whole lot that can be customized.
To change to a more versatile and customizable login manager, like KDE, you will need to install the following as su:
yum install system-switch-displaymanager
To make the change to the KDE login manager, run
The KDE “Login Screen” X interface, located in “System Settings” can be used to change the appearance of the login screen and the splash screen displayed after the password is entered.