This is a question for someone like David Baumgart (art director) or anyone who knows how Dredmor uses the tileset files for making custom tile sets in DoD. What are the dimensions of each wall piece? Is there some sort of template availiable?
Each actual piece is 32x32 pixels (which means that wall pieces are 32x64 pixels, as they are 2 tiles high). And templates are in "/tilesets". Unless you were asking about something else.
by template, i was referring to some kind of template image that would draw the boundaries of each frame.
I don't think you really need that. Unless the program you use has none of these features at all, it's quite easy to either overlay a grid or create your own with guides. Each to his own, though, so it would be good if we got an answer from David (and I hope he doesn't mind me only using his name).
