It depends on what the joke is. I can see people making an image for a joke that they already have in their head. Or they can AI generate an image and think up with a caption to make whatever it generated is funny (partially clips does exactly this with clipart). Sometimes it can be completely AI generated because the humour comes from seeing how the model misconstrued what it was supposed to do. A lot of these require humans to do the work of curation.

I'd be kind of tempted to give these box art images to an AI and ask it to make the game. I suspect there would be much amusement to be had in seeing how they do at a cursed task like that.