Glad you like the art as well! I have had a couple of different artists over the years, so the look is not as consistent as I would like, but I like the visuals overall.
I don't think I would ever use AI tools for the art, unless I was forced to (like running out of money or having trouble finding an artist to work with). I think at this point all scenes should have at least some art, unless I am forgetting something.
The game could be updated to add more content with some work, but as I mentioned I am trying to wrap things up, so it's unlikely we'll see many new maps, other than the ones I have already planned.
I probably went a little too wide with the content, but at least we got plenty of variety out of that! :)