Once upon a time, I used to be a fairly active amateur level designer, doing my thing for various engines based off the venerable Quake engine. I've been out of it ever since I shut down the old Valve Developer Union site I ran and the Quake scene got sick of me, but here we are.
All of these should run fine in a vanilla engine. Still, for my Quake sessions, I prefer Mark V, a modern engine with support for software rendering for that extra crispy look. Sources included; feel free to do whatever.
(And now, my old (2018 or so) writeups for these maps are back, so click to read and stare at more screenshots if you're curious about the story of each one.)