What does a Unity server look like?

The most that a Unity server would typically have is an administration GUI made with UnityGUI. You could output various statistics, player information, and have functions to disconnect or ban players if need be. You could also setup a camera to "watch" what the players are currently doing, though this isn't necessary.

Basically, it can be whatever you want it to be. There's no standard way to code a Unity network server. Make it however you'd like to. Be cautious though... the more inefficient your server is, the more the clients may suffer. In this respect, I would almost advise against inserting a camera or any rendering onto the server scene, though as I said, it is technically possible. :P