I'd like to see some things more akin to traditional Gaelic and some Brythonic faeries. They were often not so much outright malicious (though they often could be) so much as possessed of a very warped sense of ethics that lacked the remotest sense of empathy for others. And a lot of them just looked weird. There's a Scottish creature that had a head the size of a whale on a man's body, with translucent skin and an enormous grin. He'd wander up on beaches sometimes and consume people with his massive maw. In one story, a priest gets it to stop by offering him hospitality (he gave him a cask of wine), and asked why it did such awful things. "I'm hungry." Then it went back into the sea. Some are pretty nebulous creatures, too. Like a kind of giant hairy man in some Manx and Scottish myths is seen, sometimes, but disappears into fog, and leaves a person with a sense of unnatural dread that drives a person mad with terror, often to the point of suicide. Hill-women were some kind of vampire like being that moved in groups. One would convince a lone traveler they needed assistance. If they followed, they'd be torn limb from limb by the rest of the group and their blood consumed from the wounds, and the creatures were revealed to be the dessicated phantoms of deceased women. I use these specific examples because they all had the same severe weakness to worked iron. Touching it would cause them to die. I find it funny because it's such a plain metal. I'd like some very bizarre, dangerous, or just gross things that could die by such bizarrely simple means (given, at least in said cultures, iron wasn't exceedingly hard to come by; considering the Gaels' view of how their people came to be, with invading Ireland and all with superior weapons, it was probably just a commentary on that, but it still lead to some hilarious and weird myths).
I'd really like to see catacombs and such offering creatures specific to the cultures that built them. Think of a civilization resembling the old Norse peoples; tombs could sometimes be guarded by something akin to a draugr in certain cases. But similar beings don't exist in all other mythologies. It'd be a good chance for some dynamism culturally, giving a region more direct character in relationship to the peoples who live in it. It'd really be nice when cultures are themselves more dynamic.