This is a Megaman themed capture the flag map, that I made today. It would probably be ideal for each team to be at least 16 players because of how big it is. You can obviously make changes to cater your needs. The idea would be where you see the lines of bedrock at the spawns for each team, that's only passable by people from that team, which you could do with a plugin.

If you use this in your server, let me know, because I would love to come play on it.