I've made a few maps and I think one is still in rotation.
From my time playing, the one thing you can guarantee is troop movement. 95% spawn and make a straight line to the other side, meeting in the middle. Cavs will circle around and there's usually 1-2 ninjas who spend half the round going around the perimeter. When I made maps, first I tried to do a lot of stuff all over the map like little clusters of trees or some fallen logs to provide archer cover and shooting spots. Then I realized that almost no one goes to these areas; its always straight ahead to the middle. So I focused on making the middle interesting. Lots of cover, different avenues and elevations(not terrain but rocks/buildings/etc). And if there's a river, making a lot of bridges, both for cav and so that infantry is not forced into one narrow kill zone.
Regarding the original map that everyone hates, I don't hate it but its not one of my favorites. And the reasons are 1)zero cover along the main path, 2)forced to go into the water, 3)steep elevations. If I was changing the map, I'd add at least one, maybe two, bridges in the main area where people cross. I'd dot the landscape with either small groves of trees, single trees throughout, or rocks. I'd also probably add some large boulders in the shallowest crossing area to break it up and give some cover to those crossing.
Maybe that's a little much. I dunno, as my maps tend to grind your system to a halt cuz I like a lot of little details.
PS: I do hate the volcano map. Those poor textures were not meant to be stretched so much.
