I've done intense research on unused M&M6 features. There are three things, that seem to be bugged in the game:
1. Chests backgrounds seems to be swapped in some cases
2. Taverns in Eastern Bootleg Bay Island and Northern Eel Infested Waters Isle are run by a pirate, however their signs in front of taverns are swapped - the first is using Goblin's tavern sign, second is using rich tavern sign. Moreover Goblins in Bootleg Bay city and Southern Eel Infested Waters Isle also run taverns, but don't use corresponding Goblin signboards.
3. "Disease" condition uses "poisoned" portraits
Here you can find unused graphics that I've mentioned:
https://tcrf.net/Might_and_Magic_VI:_Th ... d_Graphics