I agree with the others that there needs to just be 1 neutral thumbnail and icon, something like what Wsly has pictured. Seeing all of these randomized, false icons is very confusing and misleading, and it should absolutely not be like that.
Aside from that, I think this is a smart change. Definitely will be good to counteract inappropriate game thumbnails/icons. Of course it's unfortunate for games with owners who are no longer around to update those images, but I doubt those games are still generating large amounts of traffic anyway.