Packages with the gdm use flag

sys-boot / plymouth : Graphical boot animation (splash) and logger

  • Enables smooth transition to GDM

x11-misc / xscreensaver : A modular screen saver and locker for the X Window System

  • Use gdmflexiserver from gnome-base/gdm instead of x11-misc/lightdm

x11-themes / redhat-artwork : RedHat's Bluecurve theme for GTK2, KDE, GDM, Metacity and Nautilus

  • Install Bluecurve gnome-base/gdm theme