Here are some map possibilities. I'm also open to suggestions. 12-15 provinces/player would be good and it would be nice to have a few water provinces both to break up the terrain and provide a chance for nations with special abilities like sailing or amphibious to make use of them.
Sixlands
Balanced and well tested. An excellent map, the only drawbacks being that it doesn't look as nice as vfb's other map (Five Lands) and I've played about a million games on it.
Threelake
I really like the look of this map and the way it plays but starting in the center area of the map is a definite disadvantage.
Greenland
Blatant self-promotion.
I made this map a while back - like Sixlands but not as balanced. Not really sure how it would play.
Post Diluvium
One of the players made this for the Myth game and I think it plays really well. I'd just remove most of the water provinces for this game (it's actually a bad situation for a water nation anyway).
Realm of Rampaging Roaches
Elmokki has a lot of good maps but they tend to have a little more water than we're looking for. This map might work, though.