Most recently I finished Japser Kent's Twelve, a story of vampires during Napoleon's invasion of Russia in 1812. Reviewers had touted it as being highly original, ignoring the work of Chelsea Quinn Yarbro and her Count Saint-Germain novels and even 2000AD's Fiends of the Eastern Front, which whilst set in WW2 has many similarities with Kent's book.
This said it doesn't make it a bad book, on the contrary it is quite entertaining, but it's not as innovative as many reviewers said. The story is well written and follows a Russian officer who finds out the truth about twelve mercenaries hired by the Russians to help defeat the French. Personally I would be liked more battle action and maybe some more story set around the actual retreat from Moscow but what you get isn't bad and the book is an enjoyable read.
Wargames wise alt-WW2 is quite popular with vampires and werewolves and reading this there is no reason why alt-Napoleonic couldn't be, especially at skirmish level maybe using rules like Sharp Practice as a starting point (Flintloque has a proven pedigree as fantasy Nap, so why not alt-Nap?).