I can agree on the lighting and colours. There is a kind of plasticky, shiny look to things while also remaining dark that makes it hard to make out at times.
Also, while I don't know about map markers, some guidance would be nice. Even a room number when you're given the key would be nice. I ended up sticking my head through the walls to try and see which door had a room behind it, because I couldn't work out which one was mine.
Personally, I wonder if the problem with the graphics might be that it's trying to look too realistic. It walks that uncanny valley too much, when the aesthetics might look nicer if it was a bit more cartoony: bright and colourful, with simpler textures?