How about a high school? I am working on a high school right now.

Make up a new mini-game. Perhaps there is a 10-block long strip of blocks adjacent to another, and there is buttons above, which if hit, The block under you goes back into the wall, so, you're shooting at the buttons above the players across, and they're shooting your buttons, and each time they get one, there is one less block for you to stand on, until someone ends up losing, at which point it is reset. It's kinda hard to explain, but I can post a screen of what I mean if I should.

a kind of zelda map with huge world and dungones with bosses. spells with /testfor and knowing when you drop a item named something. cool cities with shops and arenas. side-quests and cool items. maybe after a boss fight you could get more hearts forever (which you can do with effects ). this you might need a team for but this forum could do that.

Castle
Lakeside Home
Beach / Beach house
Amusement Park
Estate
Haunted Mansion / Estate

Hope this helps!

A quick Adventure map with a play time of around 10 minutes? Perhaps a story about the character trying to get a banana? Idk. Have fun with the idea though

A banana