Once in a whaile a Quake-enthused mapper will come up with a hair-brained idea of making an episode. This is what happened when I decided to start creating what eventually became starkmon.bsp. I just started piecing together brushes with those 128x128 idbase textures, thinking about how awesome it would look when loaded into Darkplaces.
Stark Monstrosity was built with the idea in mind that I was going to try and get the player lost in a maze that was some massive id-base themed map. I built a layout based around a set of hubs, which would interconnect massively. This map will work in any engine I know of, it doesn't break the limits of the original quake.exe, although I believe you would have to allocate a large chunk of RAM via a command line.
This is just my idea of dumping the player into a situation where they would have to forge there way through a large base, full of hostile enemies, with lots of machine-gunning and running around. Exploration is the key here - you will have to follow a sequence of keys and triggers in a somewhat non-linear layout.