There was a post about the cover art for Wolfe's new book some time back, but it seems to have changed. I think the new art looks pretty great, nice retro feel, though not being one of the lucky few advance readers, I can't say how well it fits the book.
Also - I wonder if there's a connection with J.S. Le Fanu's story The Evil Guest? Le Fanu isn't THAT obscure, and his Carmilla is still fairly well-known, one of the key vampire novels, etc.
Here's the Le Fanu story at Project Gutenberg:
http://www.gutenberg.org/etext/10377
-Matt