I just want to point out you might find an AI image generating service that says in its terms that the images have no copyright, but it could still generate copyrighted or trademarked content, like images clearly depicting Mario from Nintendo games. Does the fact the AI company saying "these images have no copyright" override Nintendo's copyright for Mario? It's not clear, and I suspect the answer may end up being no. In that case the AI company can't make any promises about the copyright of the generated content. They may try to claim the generated content has no copyright, but it might actually generate content which someone else owns the copyright for, which you could then get in to trouble for.
This is all speculation, but I think there could be messy consequences for some people...