Things to note beforehand: I prefer playing semi-competitively when I play ttt, so I tend to play mostly seriously, and treat maps with a competitive mindset.
Maps I enjoy a lot on this list:
Casino - The layout is consistently fun, as it works well competitively, but isn’t a free win for the traitors every round, because it can force a traitor to play aggressively, and forces you to outplay your opponents. The only notable downsides are that people tend to stay outside, which can make some rounds really hard as traitor, especially for people with poor weapons. Also people tend to stick close by, so you need good gamesense, map knowledge, and hearing to know when to make moves, and without these you will perform poorly most of the time as a traitor.
Skyscraper: This map is generally really fun, the layout is simple and easy to understand. It is one of my favorite maps to play on this server, because with good positioning and timing, any traitor with almost any weapon can win and you don’t need any map knowledge to do well.
Maps I think are meh:
Airbus: Airbus can be fun, but it’s a really hard map to learn. There’s a lot of rooms and that can be confusing for new players, not to mention how terribly unbalanced it is for traitors. First, in several cases there will be several people on top of the airbus, forcing a traitor to either A. Spend a credit on a c4. B. Rely on their aim and gun and make a risky play. C. Wait.
I don’t care much for this map, and it would be rated lower for me but I like the disco bar room 
island: Island is fun, and it can be played decently competitively, but its mostly just sniper/garand/sg550 heaven. It doesn’t require much skill, but small tricks can help. I don’t mind playing this map but it definitely is not my favorite.
Community Pool: Its one of my favorite maps to play, but it is awful competitively if there are more than 6 players. It becomes exceedingly hard to kill people in such an open building when theres more than 6 people.
Maps I dislike or prefer not to play:
Rooftops: This one is definitely controversial, but I do have a few good reasons as to why it’s bad.
- This map practically forces you to use a Rifle, Garand, or Sg550, and the snipes on this map are super easy to hit, since all you have to do to win the round is hide somewhere random with a rifle and pick people off.
- The skybox easter egg makes it impossible for someone to reach a player unless they also happen to know the easter egg, which is rare. Its cost many people t round’s that they could/should have won.
- This map basically makes anyone who doesn’t have an extremely long range weapon able to do nearly nothing against any sniper.
Clue: I just dislike clue. It could be extremely fun to play competitively if people didnt just stay in one of 2 rooms. Pretty much the entire round as a T is just either you make a risky play in the main room against several people, you wait until someone finally leaves the main two rooms, then pick them off, or you place c4 and get a free win. It is boring.
Waterworld: its just like rooftops. Snipers are the meta, anything else is just bad. Its hard to get clean kills without a sniper or mobility exotic like pull90 or sso.
Any other maps I dont have a strong opinion about or dont care enough to write about
As for things I think you should keep in mind when making your map, try to consider more competitive aspects of things, like keep in mind weapon ranges, try to make a map where most weapons can be used well, instead of having one-sided maps like rooftops that is very heavily in-favor of snipers.
Adding fun easter eggs like rooftops or music boxes like airbus is generally a good idea for making the map interesting. Also try to avoid something like casino or clue’s problem of having most people in one area at almost the whole time.
