Dragons of Vorndrang: I quite love the idea of Dragons bound up to special places as outlined in Terry Pratchett's The Colors Of Magic. If you're not familiar with the book, here is an excerpt from this article at Wikipedia:
"Noble Dragons are the large, graceful fire-breathing creatures of legend. Probably evolved from Draco vulgaris, these dragons use magic to combat the physical laws that would normally kill a flapping-winged creature weighing several tons and spitting burning substances. Because this requires more magic than the Discworld can in normal circumstances provide, Draco nobilis now exist mostly in a parasite universe closely connected to the human imagination. They can be briefly released from this universe by a sufficient expenditure of magic, or summoned on a more permanent basis in areas of high background magic. Examples of this can be found in The Colour of Magic and Guards! Guards!"
Mines Level: Two of them, maybe three. A complex network of tunnels and train tracks, probably on a scale much wider than usual (1sq = 50' or thereabout), with mini dungeons scattered all the way around (most likely OPDs). One of them is haunted by undead dwarfs awakened by a powerful necromancer.
Fatal Misapprehension: Do you remember the incipit of John Carpenter's The Thing? With the poor crying dog and the misapprehension that made The Thing itself survive and start haunting again? Well, I plan to do the same, only using some tough monsters hunting a seemingly harmless bunny (this is because I recently watched Monty Python's Holy Grail and had a blast).
Reworking Goblins: As Gremlins. How cool is that?