Sounds like you have numerous ideas already but if you're trying to come up with ideas for "objects" to place in the rooms you may want to think of what the dungeon is currently used for by your inhabitants (if anything) or what it was used for in the past.
For example:
- Groups of tables and chairs with dishes/mugs, or messed up/knocked over
- Beds, cupboards, bookcases, cabinets, etc. You could scatter these around without the rooms looking "specific"
- Piles of disused/broken equipment, furniture, bodies
- For floors/walls: Torn tapestries, ye olde maps, scrolls/documents, fire scorches, spilt flasks
- Archery ranges, combat dummies
For example:
- Groups of tables and chairs with dishes/mugs, or messed up/knocked over
- Beds, cupboards, bookcases, cabinets, etc. You could scatter these around without the rooms looking "specific"
- Piles of disused/broken equipment, furniture, bodies
- For floors/walls: Torn tapestries, ye olde maps, scrolls/documents, fire scorches, spilt flasks
- Archery ranges, combat dummies