Unless you don't actually care if everyone sees the same results. So long as the generated image is approximately what you prompted for, and the content of the image is decorative so it doesn't really need to be a specific, accurate representation of something, it's fine to display a different picture for every user.

One of the best uses of responsive design I've ever seen was a site that looked completely different at different breakpoints - different theme, font, images, and content. It's was beautiful, and creative, and fun. Lots of users saw different things and had no idea other versions were there.