This last month's SCBWI meeting in San Diego was a panel discussion about diversity and inclusion. They provided some interesting stats (see images here) and a wonderful video found here. The panel was primarily about writing children's books, not illustrating them.
The biggest take-away that I got from it was the concept of "windows" and "mirrors". That as much as young people want to read about people like themselves, they also want to read about people who are different. Creating diverse books is sometimes about providing windows for children to look through at others who aren't like them, and sometimes about providing mirrors in which they can see themselves reflected back.
Regardless of whether it's a window or a mirror, we have to have a basis of knowledge and research (some might say experience is stronger) from which to draw upon so we are actually being authentic and true in our stories.
One of the panelists, René Colato Laínez, said something very interesting. He said he was given advice from an editor that he never forgot. She had told him that when writing stories about a specific culture or minority: if you can take the names of the characters and change them to a different culture (like making all the characters French instead of Latino) and your story isn't impacted or altered, you're not actually writing a story that speaks to the experience of that culture or minority.
In my head, that meant: If you're writing a fairy tale that takes place in Russia, make sure you're using Russia on purpose and not just as decoration. I suppose the same thing can be said about illustrating: don't do something purposefully in, say, a Japanese style, for example, without knowing the why's and how's of the authentic style you're drawing upon. Otherwise you might be communicating information and mistakes you don't realize you're making... (I think that's the definition of cultural appropriation--using pieces of a cultural expression for your own derivative purposes without respecting or caring where it came from or what it might mean or what you might inadvertently communicate...)
Not all stories fit that paradigm. But make sure your choice to include characters of varying ethnicities or cultures or whatever doesn't contradict itself. Do your research. Hire a Sensitivity Reader like you would an Editor for your work. Ask friends from those communities if your work rings true and is non-offensive. 'What we don't know' can inadvertently be a big deal.
One other thing they did mention was the #OwnVoices movement and the inverted version of it that some seem to use against it: the idea that people of a specific minority are the only ones capable of writing stories or illustrating authentic characters from those minorities, and that given the interest in writing that embraces diversity (in 2015 fifteen publishing houses announced new imprints specifically for diversity titles), there is no place for white writers. That is simply not true. But if your goal as a white, 55-year-old male is to create a story about the experience of being a black woman, don't be naive and think your sympathy equates empathy. Respect your subject enough to strive to tell the best story in the most authentic way you can, and that means making an effort at hearing (and actively listening) to their voices and seeking out their expertise, perspectives, and impressions of your work.