/etc/X11/xdm/Xsetup_0 is hard-coded to put up a Red Hat
banner, but it ought to run /usr/bin/kdmdesktop if KDM is
being used as the display manager.
As shipped, 6.0 has a uniform background for GNOME, KDE, and regular
xdm. However, we will work to make kdmdesktop at least an option in
6.1. This is more feature request than bug...even though some KDM
functionality is purposefully disabled, it still functions fine.
However, you have a point and we will try to find a flexible solution
that still unifies the various desktops we include.