Eh... smart way to do it would be to have some of the rooms flip to the Upside Down variant while you're in them. They kind a hint at it, referring to going into the Upside Down "whether you want to or not."
Scareactor hits an e-prom that switches the "normal" lighting to blue/purple upside down lighting (that reveals vines painted into the walls), waits a beat, then pops out. It's actually REALLY easy to pull it off.