The tag is "FNAF_Background". It's not a replacement for describing the background, rather it mostly alters the pallete of the scene to fit a murky FNAF location. This lora was trained on character-free backgrounds from a mix of FNAF 1, 2, 3, SL, and UCN. It was created with Anything-v5
Also this may sound counter intuitive, but sticking "FNAF" in the negative tag can help make characters you put in the scene more accurate. This is because I foolishly decided to put FNAF in the tag name, and that count towards the prompt.