Why nothing appears
The decision to keep the frame empty is not a limitation, it is the technique. A shown monster is a fixed quantity — once you have seen it, it can only get less frightening. A room behaving wrongly stays unresolved, and the viewer keeps supplying the cause. Locked-off framing and a slow retreat reinforce it: the camera is not looking for anything, which implies it does not need to.
Choosing a room
Practical lights in frame are the single biggest factor, because flicker is the primary event and it has to be visible. Lamps, a ceiling fitting, a lit doorway. Soft furnishings — curtains, a hanging plant, a tablecloth — give the second layer of events something to act on. A bare, evenly lit white room has neither, and tends to produce a clip where very little appears to happen.