Regarding the usage of AI Art for TEMPORARY PLACEHOLDER AND REFERENCE PURPOSES ONLY (for those leading to conclusions the moment they read "AI Art"). I personally do not support the usage of AI Art in any shape or form no matter how big or small it is, mostly because of the ethical connotations linked to it. Unless you can prove that you asked for permission to the artists whose art has been used to make that Ai-generated image.
As an alternative however, you guys can use stock images instead, and then stylize it the same way you did for the AI Art. Sure, it wouldn't be the exact way you envisioned it to look, but its otherwise better than potentially infringing on other artists' works.
Overall, while I understand the difficult position the team is currently in, there are still other ways to tackle it without resorting to AI Art, but I do not blame the team either for looking into it. I appreciate that you approached your audience about it!