To allow for configuring of your login screen you can open up the
Add/Remove programs screen, go under the X Desktop menu and take the check out of the box by
gdm ( this is what RH uses as default, I've never figured out how to change this one ) and once gdm is removed then the
kdm login manager will be the default, since you are using KDE you can then go under the login manager under the KDE Control Panel as root and customize to your hearts content.
Good Luck