That sounds like a nice idea, but I’m doubtful that many developers would put in the time and effort to put something like that together. (I’m still seeing uploaded screenshots in different resolution for the same game quite frequently…)
That being said, if you already had a template prepared you could pitch the idea to individual developers on itch. Maybe Star West of itch.io fame would be interested in collaborating with you on that.
At the very least 77 itch.io users are very into the idea of nice, standardized templates for developers and other artists to use - so I think the idea of developers uploading those print out covers as a “goodie” will find some traction.