Concise description:
I think it would be cool/useful if every map was classified as a standard map (basic bonus rules, maps of continents/countries/cities/basic fantasy maps, maybe like autodeploy for a capital or something is ok) or a special rule maps (weird rules, i.e. if you control Darth Vadar and his lightsaber you get one bonus army....sorry, star wars was on tonight).
Specifics:
Obviously the tricky part about classifying the maps will be where to draw the line. This could be up to the maps creators, the foundry, or the people of the forum on a map by map basis. Another way might be to set specific rules that a map either falls into or doesn't. Sorry for suggesting a somewhat open ended idea but i think if the details can be worked out it would be worth it.
This will improve the following aspects of the site:
Searchability. It would be great when going to gamefinder to only search for basic maps or only for wacky ones. You could also work it into the random map feature and make a random map setting, a random standard map setting, and a random special map setting. There might be other advantages to classifying maps that I don't see but that might become apparent with time.