Check out the Coagula maps by Tim Elek (and the subsequent coagula map packs other people made) for one of the most unique trends in quake map design
Zerstorer is great and almost overambitious
Underdark Overbright, the map pack included with Copper Quake, is worth checking out (but it needs copper to run)
Travail! I haven’t finished this one but what I played of it was extremely good looking with uniquely labyrinthine outdoor environments
Neil Manke’s early levels (especially Spaceship) are extremely cool
A Roman Wilderness of Pain is just an absolute joy to play
1000 Cuts is a really cool idea for a quake level, it has branching paths!
this is very preliminary, just thinking on memories