Workshop

Unfortunately, the film only covers the first two volumes out of 11, and the books are too "adult" to include illustrations. And as I said, I'm not an artist and I can't draw. I can do it without pictures if they are so annoying!

No, it's better as it is. Although, I would like to point out that there is a way to improve the situation. It's up to you, of course, but I would do one of these three things:
1) I would find "realistic" art for all the characters that are not in the film. That is, not doodles, but an attempt to draw the character as close to reality as possible. The remaining arts, which are from the film, would be processed with a filter in the style of an oil painting.
2) I would find art for all the characters that is similar in style.
3) I would only use frames from the film, and for the characters that are not in the film, I would choose based on the principle of "also frames from the film, but not that film and not those characters, just similar ones".