The random maps can also be created separately.
In fact most of the games on my server use randomly generated maps but they arent created by just telling the game to make a random map. The map is created first with specific settings, and then the game created using that map.
Just to note it here, when I was setting up a random generation system for Dom3Minions.com I had to come up with new names besides to add to small, medium, large.
http://www.dom3minions.com/RandomizedMaps.htm
The range on the Dom3 internal map generator is 10-1500.