The premise I am working with is that the original cellar was much smaller than the existing dungeon and was simply storage for a small roadhouse. Some nefarious party or individual converted the roadhouse to their own purposes and turned the cellar into a place to house unfortunate victims prior to finding other cruel purposes for them. The rest of the dungeon was expanded over the years to accommodate other activities. I think I'll build it outward chronologically to see if I can make sense of it.
Here's the original cellar with floor texture and spiderweb. It still needs the rest of the objects described: cage, manacles, and doors. The other items are movable and will therefore not appear on the map. At the rate I am going, I won't finish this map by the time the challenge deadline is up, but at least I am learning quite a bit in the attempt!
Once again, the thumbnail is bizarre, but the actual png is fine.