Horror Cinematic Universes
I've noticed a cool little trend popping up in horror films where it is clearly stated or heavily implied that there are other, much bigger spooky goings-on in other places with the same events or with a completely different scenario. Very much like how Stephen King would tie all his books together with little bits of lore and hints. The horror situation doesn't necessarily have to tie in with the bigger picture, but just getting that *feel* that this or some other horror movie scenario is going on somewhere else in the world is such a cool idea and always leaves the viewer questioning what else is out there.
Examples would include, Obsession, Oddity, Caveat, Talk to Me, Bring Her Back, Weapons, and Hokum.
I think it's interesting enough that it leaves room for discussion and intrigue, but without needing to answer all of the viewers' questions and leaving just enough open for them to wonder what else could be going on.