If the artist makes the image very similar to one of the reference photos, it may be a copyright violation. It doesn't matter if the artist used a pencil or software to create the new work.
Current AI image generation does, however, make it easy to unknowingly violate copyright. If it generates an image similar to something else out there you wouldn't know.
I don't know much about copyright law though, am I wrong?
You can claim intellectual property for comic characters etc, but not photos.
YOu could get someone to go get a similar photo taken at the same place, and use tools to enhance it