[gpm]

What percentage of people will notice the primary means of marketing the film?

Almost all of them, surely. Maybe not consciously... but unconsciously certainly.

Films are incredibly expensive products to produce, an average of $100 million dollars apparently [1]. Do the incentives really not align to pay for professional artists to create a high quality thumbnail? I doubt it. Hell, youtubers have figured out it's worth doing this on every video which cost and pull in 4-5 orders of magnitude less money.

[1] https://www.investopedia.com/financial-edge/0611/why-movies-...