I know a lot of people have problems thinking of a map idea, and all the guides have more general ideas that are like this: RPG map. In this guide, I will show some specific ideas like this: A RPG where you have to get a legendary wand.
1: A museum heist with a vault, lasers, and display cases.
2: A game where you run a bank or shop.
3: A RPG game where you have to obtain 5 gem shards to craft a legendary crystal.
4: A obby where you have to escape a pet store or barber shop.
5: A protect the sentry game where you buy barriers to stop the invaders from knocking out the sentry.
6: A game where you guide a traveler to a forest or town.
7: A game where you test a player’s skill by letting them select a boss to fight/ a SBBF game (Skill Based Boss Fight)
8: A game where you protect a train carrying a valuable diamond.
9: A underground escape room where the walls are caving in, so the player has to rush to beat it.
10: A game where you get a job at a hotel, or you stay in the hotel.
11: A disaster RP with maps and disasters like these: Tsunami, space meteors, volcano, and forest fire. (I didn’t say flood or earthquack because those are really hard to make in gimkit.)
12: A game where you are trapped in a mountain and you have to escape by getting through puzzles, monsters, and obstacles.
I hope all these helped you find a new specfic idea to build in gimkit! 
These next few will be reply ideas:
Thanks to @Pika_Pokemon for these 3 ideas:
1: A maze with traps and puzzles or just a escape room mixed with a maze.
2: A protect the prop game (the same as number 5 but use a prop.)
3: A mystery where a bank is robbed and there are two suspects: You and someone else.
Thank you @Blizzy for these ideas:
1: A protect the player map. (more details in post 7)
2: A prison RPG where you make deals with your cellmates and the guards to help you escape!
This is a idea by @Bobthebuilder123:
A horror game where a monster will try to destroy the players, and the players have to survive untill sunrise. (5-7 mins)
This one is a idea from @ClicClac:
1: a
This will be another one by @Bobthebuilder123:
A game where you have to occupy all the occupation points around the map, while defending your occupied points.