Like the sketch and I also like the idea that some gnomes broke through into some monster dungeon and got... predated.

Just want to point out that there is no need to fill all of the square areas right to the edge. Not that its bad to do so but just that its not a requirement. We can place the maps together on a single grid basis not as a whole block like a geomorphic dungeon. The smaller and more irregular the bits the more interesting the fit up can be.