I've been toying around with an idea for a level that could act as a hub somewhat between multiple levels, and clusters, though with limitations where you couldn't really enter a cluster you hadn't yet reached normally. (In the vein of a couple here where the person would die after an hour or so of being in the wrong cluster.)
So, here's the basic idea:
People are regularly dying in the Backrooms. However every tale or story suggests that no remains are found. Based around this I would propose a neutral entity and rooms which they occupy, with their duties being the cleaning of the Backrooms, maintaining them, and disposing of bodies.
The room itself would be similar in a way to the Pipes level, but differ in that it has a number of incinerators, and crematoriums for the removal of the dead. Some rooms would be filled with cremated or burned remains, and the overall network of rooms would seem to loop back on itself, with a handful of doors that when opened would lead to various rooms, though also some doors open onto hallways that lead back to where the person was originally, though through a different angle or area.
The entities would pretty much ignore survivors unless the survivors in the Backrooms try to stop the entities (I call them "Burners") doing their work. Get in their way too much, and you could find yourself shoved into one of the many incinerators.
The room would also have a number of standard entities, though interaction with the Burners would be curious for a survivor. In that the entities are seemingly afraid of the Burners, and would go to great lengths to avoid them. I picture the burners being dressed in a full body white coverall, with latex gloves on their hands, heavy boots on their feet, and a WW1 style gas mask that covers their face.