OpenSUSE is a different beast than the FreeBSD I know and love. It seems that in order to run the Desktop Environment of your choice, you do not edit the /home/.vnc/xstartup file. That would be too easy… It seems that Gnome runs its own implementation of VNC; it uses vino-server for remote desktop services. This is evident if you run a netstat -ap – check it out:
Anywho, it seems that the easiest way to configure this is to utilize the “Remote Desktop” applet included in SUSE’s application browser and Control Center. This will allow you to run a GDM desktop over VNC. It seems that this vino-server takes control over the gnome-session manager, and will not let other programs execute it. Good luck!