I imagine the financial security R&M brought Spooky via an insta-sellout (rather than a long slog through uncertainty) is something they'd to try to replicate. The best chance for that is continuing the move toward more broadly popular IPs than more niche ones. That would disqualify all but a handful of pure horror licenses (Nightmare on Elm Street + Friday the 13th), if even those. The first Scream was a cool movie and I know there are others but doubt people care about them, so that doesn't feel like an iconic "franchise."
Comedy + Horror/Fantasy expands the list a bit. Tim Burton titles (Nightmare Before Christmas and Beetlejuice) could definitely sell a thousand. Evil Dead / Army of Darkness probably too, given its cult fandom.
But out of all of those, I actually think Scooby Doo would be the best option, which I find surprising. I don't sit around watching Scooby Doo, don't collect its memorabilia, and haven't watched it since I was a kid. But the memorable characters, voices, and music, colorful animations, and basic tropes (different mystery monsters to unmask) lend themselves well to pinball and align with the "spooky" brand. Plus they're perfect for kids while nostalgic for parents and can support grown-up winks to adults.
For whatever reason, I'd rather play Scooby Doo than any pure horror pin. Not saying it can't be done, but translating horror to a repeatable fun pinball experience just seems much tougher than with other genres.