Wait, an adventure set in an asylum that's NOT horror or supernatural, you say? What sorts of plots / challenges / vibe would it have?
Because I would probably be sorely tempted to bring in horror or supernatural stuff if I made an asylum adventure. I've GM'd that genre a lot, having run adventures like DCC's Gates of Delirium (with it's own soundtrack by Midnight Syndicate!), the CoC advanture The Asylum, and some home-brewed adventures.