Quake 2: Secret room - The Id Gallery

On the last level, after you completely destroy Makron or whatever his
name is, and you get the message that you need to find an escape pod, don't.
Not yet.  Hit one of the two buttons on the floor again and go down into the
room under Makron's main chamber.  There you'll see a crack in the wall
that wasn't there before.  Blast through it and beyond is the Id Gallery, with
photographs of most of the developers and another odd little scene...