Minecraft wiki entry for Creating_a_challenge_map, associated text: Theme of the map; what it will be about
Type of map
General storyline (if any—used more for story-based adventure maps)
A basic outline of what traps, challenges and dungeons you will put in (what they are and where they will be)
Basic blueprints for any large structures that will be put in the map
Redstone contraptions tested in another world.
Loot and rewards the players will gain along the way