Can I have a different display manager (greeter) on different stations?
No. It is standard to all Linux that the display manager is controlled on a per-system (per computer box) basis (i.e., per system not per station). Hence all stations will share the same display manager (e.g., K{Desktop Multiplier}, GDM, etc.). Users of course can choose their preferred desktop environment (e.g., Gnome, KDE, etc.). And you can change the default Display manager for your system in the usual manner. Consult the documentation for your own particular Linux Distro.