Rabbit hole Exhibit A:

Category posts are assigned images for preview cards ∴ posts without any images oughta default to a their category's image rather than a site default image.

Posts can belong to more than one category ∴ it would be cool-as-f$&k if all a post's categories were represented in the preview card image.

Ooh … ooh … I bet I could stick the category images under the assets directory and, using the Hugo pipe image manipulation API, generate these hybrid preview card images on the f$&kin' fly…