What's inside the Shady Sands houses

[Grayswandir]

Most likely any tile over 4096 would not register in the mapper, but who knows…the world might just end.

Yep. But then again, there is this possibility that the game and the mapper have differents limits, so you could just replace old tiles with new ones on the mapper, since changing objects on the mapper doesn't affect the ones already on the maps.
But i never tested it over the limits, so I wont bet my head on it.

It's especially easy for the tiles since they don't have any description, a bit more harder for the scenery, don't replace a toilet with a door!