Overiding Tileset Amounts?

Is there a way to overide the maximum number of tilesets in a particular map?

I remember the map "Nature's Call, Circle Defense" did so in its terrain.

I believe, World Editor Unlimited (might have been replaced with a updated one) allows you to have a few more tiles in the tile-set. Also, you can use all the terrains if you trigger it.

NewGen can do it, up to a max of 16 tiles.
While WEU can also do this, it is not recommended to use WEU.