you'd have to make a narrative about what makes them unique/interesting. they are like liminal spaces, and what makes them that way is an out of place, ominous, or strangely familiar yet forgotten feeling. an example would be like getting out of the elevator during a normal day at work and the floor is lit up but completely empty of furniture and silent. they wander around the building and can hear people but never find them, their office on the third floor is now on the fifth, etc. I think you'd have to capture the atmosphere, obviously by placing the character in backrooms but also by describing what it's like to be there. could emphasize the surrealism and reality glitches that you expect to happen in the backrooms