I don't mean to intrude on this comment but I noticed you brought up AI. I think if you're making a test game, or just looking for placeholders, you can use AI, I suppose. But try to consider for a fully released project, or something you intend to leave a lasting effect on the player, you should opt for human created assets. AI should be a tool, not a replacement. And it also takes the fun out of picking a style for your game too.