If a game reaches 100 rounds a natural disaster occours at a random place on the map.
Sorry if this has been suggested befor. I searched somewhat but couldn't find anything. Basically my idea is that every one hundred rounds or so something bad happens somewhere on the map and wipes out armies or reduces them by a high percentage. This would create opportunities and help to break dead-locks. Different maps could have different disasters such as floods, blizards, tsunamis, earthquakes or even meteorites.
This will benefit players of the site by breaking the dreaded cold game deadlocks, 500+ rounds is just to many.