Some times, the automatically chosen thumbnail contains a black screen or just focuses on the worst possible frame to choose. I'm assuming there is some algorithm that determines the thumbnail to choose based on some heuristics, but in the worst case you can get a black screen as a thumbnail, which kills possible engagement other than users inspecting it out of curiosity. It would be awesome if users could, say every 24 hours, hit a button to randomly obtain a new thumbnail from the project itself.