What a perfect idea! These are evocative pictures that are perfect for an adventure or system that is missing art, such as Liminal Horror (what I used them for, initially), or for hiding traditional Monster Manual or Bestiary creatures behind another picture. Despite the firm tone of the pulp sources, there is plenty of choice here: you can easily find something that does not feel pulpy, if you a re not going for that.
itch.io is an open marketplace for independent game creators. It's completely free to upload your content. Read more about what we're trying to accomplish and the features we provide.