Also have a tiny bathroom.
Just figured out what to do this year... it's a Butcher Shop. Got a cheapy sign from Dollar Tree...
Got some painter's dropcloth plastic (the really thin, filmy stuff) from the dollar store that will be hung in strips from the ceiling down the hallway to the bathroom. Guests will have to push through it to get to the door.
Inside, red lightbulbs. Black plastic hung from the ceiling on the walls (dollar store table cloths). Dollar store severed hands and feet scattered about on the counters with blood splatter (clings) on the mirror.
A super grow bloody skeleton (got at Michaels $2) that grows to be at least 2-3 feet long in the tub, with a bloody shower curtain. Severed head hanging by its hair from the shower head. A "bloody" handtowel (will use acrylic paint to stain a new white towel) to dry their hands, and a garland of knives will hang across the mirror.
Sounds will be chainsaws, sharpening knives and maybe even some jaunty "musak" like what is played in grocery stores.