The ending to Back to the Future 2 was actually more of an ending.
The problem they had with the book was solved and they didn't need to go to 1955 anymore.
The ending of A Vampyre Story just happened as they where travelling between locations.
They could've at least made an animatic showing Mona at rest in her coffin, or saying, "Well, that's that problem solved, but I have a feeling this is just the beginning..."
Although that would've sucked balls too come to think of it...
Bound only by the paper thin wrapper of mortality, a soul here lies, struggling to be free, and so it will thanks to a bowl of bad gazpacho and a man named Calavera!