A little investigation by Jerrie at the Round Table confirmed the names of two additional Heroes V towns, the Academy (which had previously been mentionned in the storyline) and the Dungeon. By switching the name of image files on the official site, he came up with two very interesting pieces of artwork. Take a close look at what the Elf holds in his hand in the Dungeon banner. Isn't that some kind of rifle? Is Ubisoft trying to introduce technology elements in the Might and Magic universe?

Edit: The final town, based on nature, appears to be called Sylvan. Kudos to Sir Charles and Jerrie for finding this (in the source of the official site) almost simultaneously.