I've got a lot of suggestions for maps I used to love when I played actively 3-4 years ago. I'll write in short about some of the fun stuff about them and how I remember rounds going on them. I think they're all worth at least opening their workshop page to look at some screenshots and reading their description
ttt_community_pool_2017
Just an overall really popular map that's fun to play on. A few main large rooms where most people gather, but also some small office/bathroom rooms that allow for sneaky kills. Multiple t-traps (like turning the lights off or electrocuting the pool), t-tester and t-room.
crummy cradle
This one definitely looks weird at first glance, but I think it offers some fun notions that other maps don't have. Most of the round is spent on narrow bridges in the sky, though there are rooms spread around and a 2-3 buildings at ground level as well. Lots of verticality and open sight-lines allow for sniping, but you're also fairly exposed and it's easy to get cut off from escape routes (since most rooms are only connected by a bridge or two). There's a machine that turns bodies into bread that heals players, and I'm pretty sure T's can combine C4s into a mega bomb that blows up one of the buildings on the surface.
ttt_metropolis
Inspired by the more popular rooftops, It's square in shape with buildings across the perimeter and only a few bridges. Every building offers its own form of cover and there's a small amount of rooms you can enter as well.
ttt_desperados
A map in a desert canyon with buildings going up the side of a cliff face. Just looks cool and while it probably won't be the most popular I think it's a fun variety pick.
ttt_richland
This is more of a personal choice but I really believe the old version of richland is better than the version in the server. It's got that old vanilla TTT vibe to it
ttt_datmap_v2
A map that is built out of a mishmash of different tilings/themes and purposely has some weird geometry to it. Fun to walk around in and it has one of the most fun T traps I've ever experienced - explosive turtles.