That's true. But for one, you're not going to use all the terrains for the tileset (Unless you are, the more you do, the more work you have anyway). Second, you're not even going to program all 50 of them. I mean seriously, how many different backgrounds are you going to have for InnerBody...? It's just a suggestion anyway, using only one module is indeed more convenient depending on how you change battle backgrounds overall in the game. The way with the multiple modules would just make it easier if you're going for a lot of specific tiles with backgrounds...