More civilizations in session (Sid Meier's Civilization 5)

Is there any way to add more than 22 (or how many is the maximum) civilizations in one game (Session). I heard someone launch sessions with 41 and 60 civs at a time, which were controlled by the AI. So I want to stuff them a little more, otherwise the 22 civs are somehow not enough. Even by the end of the game, there is often a lot of no-man's space left, but you want to fight for every square.