SOLVED

Are there any tiles that match the shape of the hole in TG11Doorway? I've been looking through existing dungeons in the game for any that use this tile but haven't found any so far. I've also been looking in the caves tileset but no luck there yet either.

UPDATE:

I was so focused on the shape of the hole I'd overlooked the 'Doorway' part in the name. I finally found one in use by "ImperialSewerSystemImperialPalace" called "TG11TheWayDoor". A bizarre setup if ever I saw one, but it seems to be the only thing that works.