Hi. Yes, you're correct that the snapshots appear generic, and don't look like they contain any copyrighted content, or content that is specific to a particular game franchise - that is exactly the goal. I can't provide a catalog of snapshots for every single PC game that has ever existed, but what I can provide are snapshots that are "close enough" to the games people download.
Gotcha. Unfortunately I'm going to have to decline. A lot of time and effort went into the art for this game and we don't want the artwork to be used as generic placeholder artwork representing other games like this. I would recommend searching itch for some art asset packs and using those to construct the generic snapshots for your game launcher.