This would be nice such as xmas holiday route, but driving one AC440CW in halloween livery, and can going outside/inside of house whit halloween decorations
A train set up as a haunted house walkthrough would be awesome, but I could see it making the licensors skittish.
Just had another idea: A passenger run starts as normal, but then the interior lights go out and the train becomes a high speed express, because every station it passes is overrun with zombies and such (different theme for each station).
Rolling stock suggestions for Haunted Halloween Express: flatcars with bales of hay, Caboose with Halloween decorations mandatory (bonus if passengers in caboose), boxcars that when opened show crates of pumpkins (with a couple open to see pumpkins). And somehow David S. Pumpkins makes a cameo in a scenario.