Note to myself and anybody who may have to create the map:
40 civs mod: http://forums.civfanatics.com/showthread.php?t=234779
important explanation about this:
The 18 civs are hardcoded in the CvGameCoreDll. Without a new .dll, you can't get more than 18 civs on the map.
There is one 3.19 .dll for 50 civs in the database, you can use it.
If you then look at the scenario files/maps:
Normal maps have all the slots for 18 civs in them, even when they are "empty" (but they are there).
If you use a more civ .dll, then all these slots have to be added via a texteditor, because without your maps/scenarios will just crash.