I really like the tile set and I got it a while back.
Seeing your rectTile Universe, have you thought about making hexs?
From my experience you might want to have a repeatable section in your tile sheet asset that you can expand upon. For example you have a core section of tiles in what ever format. Then the themes expanding down or to the right repeat tile placements. So a japan and greek house will have the same location when you subtract their offsets as if they were in different images.