Comment 8 for bug 821553

There is no arbitrarty limit on the number of terrains that can be defined in a world in the branch. Also, as long as you do not rename a terrains name, all old and new maps should stay compatible. Right now there are ~60 terrains defined (64 from all worlds, but there were some duplicates like lava and some water terrains), but nothing stops you from defining another 60. :)