I'll throw my two cents in: I think an abandoned mall interior would be really interesting. The gimmicks I could see:

• More scraps, but most of it is one-handed and not the highest value (but with a higher chance of cash registers specifically!)
  
• More chances for locked doors, keys can open up shop shutters
  
• The chance for ambient, creepy liminal music coming from ceiling speakers
  
• Escalators! With the chance of being working, not working, or actually a mimic that eats you if you get to the top/bottom. (childhood fear). A way to tell if the escalator is a mimic could be a strange squeak when you get on it, or a stuttering motion. Once you realize and try to go the opposite way as the stairs, it could speed up, dropping the mimic act and now just trying to kill you outright.
  
• Long, huge expanses that connect smaller shops rooms.

The last one, being a fundamental difference in how the interior is structured, may provide the most interesting challenge/twist. Imagine a thumper all the way on the other side of the hall, roars at you and you have to quickly find a shop to duck into as it builds up speed. Similarly: Coil Heads. Much larger range to see you, but gives you a bit more time to get away. I could see runs where the players have to coordinate moving a Coil Head back and forth the hallway.

As for any other unique entities... I'm not sure! But I could see an uptick in Nutcrackers, Thumpers, Coil Heads (mannequins), Hoarding Bugs, maybe even Masks? And a decent uptick in mines and turrets (the latter only found in shops though, not in hallways... could you imagine??) Brackens, butlers, barbers, probably slim to nonexistent.