If youtube is to be believed, thumbnails make a dramatic difference to first-glance engagement. A model trained to find great(by what metrics?) screenshots from the film sounds like a fun project.
I'm looking forward to classic movies with AI-generated thumbnails that take the main actor or actress and make them do the "Youtube Thumbnail Surprised Face". Imagine The Maltese Falcon or Citizen Kane but with thumbnails that look like [1].
https://netflixtechblog.com/ava-the-art-and-science-of-image...
https://netflixtechblog.com/artwork-personalization-c589f074...