After walking around the map, I have noticed a few black figures and bloodstains. Chances are, I missed some, but I got screenshots of all of the ones that I could find. The small amount of encounters were honestly disappointing, but once again, chances are, I missed a few.
I am not sure how to put images in a discussion, if someone could help me, I'll gladly post my evidence.
I should also note that on the stairs of the final floor, you can clip into the walls and enter the backrooms.