I had a crack at my first Dungeon recently. It's called the Spider due to the fact that it is shaped like one!
The endzones are close to each other in the middle of the Spider's body, but separated by a wall:

Four of the eight legs have chests and the other four have teleporters in them:

The other two chests are in the head:

The body is quite open, but 2 doorways control access to either side of the map. There are also two teleporters on either side of the dungeon, which provide potential quick movement around the map. A moat cuts both sides in half, but the ends are not blocked off and there are 2 bridges allowing for 4 crossing points.
The idea was to have a big map that has both open and cramped areas, with various strategic access points that can be controlled by both sides. I have not tested it yet, but I imagine that both fast and slow teams should be able to do well on it. Feedback would be appreciated.