Replace all grunts with a Tijn sprite and all Cacodemons with rnlf?
Or less effort, replace one unused environment texture with the DGC logo as suggested and either include it as a secret or perhaps put it next to the exit of each map?
How about compiling the forum avatars of all the mappack authors (and their names, if it fits) into a single wall texture, and then with some careful setting of x/y offsets we can each stamp our own map with our beautiful visage, as well as including the full texture in the final (or secret?) map as a kind of group credits. I.e something like the attachment, shown here ingame (obviously I’m using vertical mouselook, you’d probably want to have a larger room for Real Doom rendering) https://www.youtube.com/watch?v=ZE9P3XFFnmc