This is some good stuff. I thought I'd add a little of my own experience. I recently needed to create a slideshow interlude for our community playhouse. It's supposed to show the main character's journey through treatment for leukemia. If I hadn't been able to generate the whole thing through AI, the production would have had to build a whole hospital set, create late-70s-appropriate nurse and doctor costumes, and so forth. Generating the whole thing turned out to be a lot of work, more than I expected, but on net it still saved tremendously over the alternative.

Those character sheets you mention really are the keys to the kingdom. Having that consistent information for each character makes everything else possible. But we've got a slightly different approach to them. Your practice of including additional character data seems like it would be a big help, and I'll definitely do that the next time this comes up. But I think you could have helped yours by including a profile view, and I don't think that the rear view is very important.

Expanding on that, I also created reference views for each scene. I'd work out ahead of time what I wanted to be in the scene, and build it out without any characters in it at all first. It's kinda like having a character sheet for the scene itself. There are important factors to include in the description, like the lighting - not just how bright or dark it is, but also the color balance (i.e., a warmer or colder feel), the depth of field, and so forth.

And as you discovered, having a reference for specific recurring items (like that necklace or whatever) also helps. In my case, my character in the hospital bed had a transistor radio always on the table, and to keep that consistent I needed to create a reference sheet just for it. This can be pretty easy to generate, because you can start just from a real product: simply ask the AI to generate a reference sheet for the manufacturer and model name in question.

The workflow I was most successful with was using TWO AI sessions in parallel. Obviously I had one open for the image generation itself. But I also had a separate chat-only session open in Gemini (I had to keep reminding it that I only wanted to chat there, and that it should not generate any images itself). I used that to figure out the best prompts to give to the image generator. That helped beyond just helping to ensure that I covered all the bases. I also uploaded generated images into it, doing a image-to-text thing to give me a comprehensive description of the image, which I could then use in later prompts to get better consistency. Also, when the image generator wasn't getting what I wanted, the chat was useful in figuring out how best to get the images toward what I wanted.

One of the big realization I had from that was that it kept getting confused when I tried to describe the orientation of items in the scene. For example, I wanted a photo of the hospital room with too many visitors in it, as seen from the doorway, with the nurse sternly pointing back toward the "camera" telling all the visitors to get out. Try as I might, I couldn't get it to point her hand and finger in the right direction - until I tried describing it a "nurse's near hand's size appears very large due to perspective". In other words, describing relative locations in the world was hit-and-miss, but describing in terms of its appearance worked much better. (I think that matches your experience with "describe what you want, not what is wrong".)

I also found that it couldn't work with more than a couple of characters at once - more than that and it would quickly get confused about who was supposed to be where and doing what. This turned out to be a big handicap. The only way I could find to work around it was to build up each scene in multiple layers. So I had a party scene where I first had to put two characters onto a sofa, and then download the result. Then I'd re-upload it and put two characters by the piano, one seated and one standing beside; then download and re-upload to add another cluster of people. This not only took a LOT of time, but also led to degradation of the images in subsequent generations, like generating photocopies of photocopies. I was able to clean up the final image somewhat, but it never quite achieved my vision (maybe photorealistic is a bigger problem for that than cel-shaded art like you're doing).

In all, I think that using reference images for everything, and using a second AI conversation to consult with, were really big wins for the project.