The first image looks better. Also it does not scream AI. Except for the missing finger.
Mostly it carries more information about the game. The second image only transports the information of "pixel art". Ok, the text might carry information, but that is trivial.
Unless that information is only the mood. There are skeletons and mirrors and bloody axes and whatnot in the game, are they not?
You could use the screenshot from here as a basis for your cover image. https://itch.io/t/4891726/pesadilla-en-san-vicente-a-narrative-adventure-game-sp... You do not need a cover for your game's retail box. Because that is what the first image kinda looks like. 80s/90s game cover, which has nothing to do with actual graphics in the game.
The second image gives the feeling of that game being at night in the hills. Slenderman stuff.
Anyway, AI is controversial. If you do not have a good reason to use it, don't. Not having the money to commision assets is such a reason, but it has drawbacks. If it ads to the game better than stock assets, meh. As you said, it gives ability to create a game, where you would not be able to without those tools. Not unsimilar to how you rely on rpg maker to actually have a game engine.
If the game does not feature AI things, you should not use it for cover image or texts. It puts your game in a category for many players.