Anyway, I thought I would take a stab for a completely different style than I have ever done. I like hand drawn (duh) so I wanted to draw it by hand and then shade/color/etc to give it some depth and make the stone walls stand out against the floors.
click to embiggie
This is just a quick test, took maybe five minutes to draw and then maybe fifteen minutes to clean, shade and texture. Kind of neat and I do like the final look, just not sure the payoff in time would be worth it. I think a large dungeon could be very time consuming. I made a few mistakes here and there but I wanted to see the overall effect so I did not care too much about the details.
This should somewhat solve the comment from +Robert Miller about how they never use an interior wall for the wall of two rooms.