The world of Vampyr is very interesting. We got a timeline that spans from even before King Arthur's time to the early 20th century, and Skalls and Savage Vulkod do look like ghouls and werewolves respectfully.

In that time is it possible other creatures might be around? Like mummies who've been around since the dawn of human civilization. According to William Marshall there are accounts of a strain of vampire that looked like Harpies, beaks and talons and wings.
So what fo you guys think? Are there other monsters or all monsters some strain of vampire?

I believe there are other monsters in the Vampyr Universe. The reason why is because in London Dr.Reid was only exploring how the Spanish flu and Vampire infection were connected. He did not seem intent on discovering other creatures of the night either because he doesn't think they exist.
(SPOILERS)
Or They knew that vampires were the ones spreading the disease.