Sylvan Dell's web site.)
When I do library and school visits, adults in the audience are usually surprised to learn that authors of picture books almost never choose their own illustrator, nor do we have any input into who is chosen or what the illustrations should show (other than what we provided in the manuscript itself). An editor at the publishing house that accepts the manuscript is responsible for choosing the illustrator and working with that illustrator to create a finished book.
Why is this?
Well, first of all, editors at publishing houses receive and are familiar with countless portfolios from illustrators. Although I suppose there are authors who have access to illustrator portfolios, I doubt many of them are acquainted with the styles of as many illustrators as the average editor. From this vast storehouse, an editor can choose an illustration style that fits his or her own vision for the book.
Secondly, an editor typically has more experience than the average author in the art of matching illustrations and text, working with illustrators, and keeping the bigger picture (or picture book) in mind.
An author-illustrator (one who both writes and illustrates a book) is in a different category, of course.
When I do book signings or author appearances with my picture book One Wolf Howls (Sylvan Dell Publishing, 2009) I hear a lot of comments on how perfectly the illustrations complement the text. People assume that Susan Detwiler, the illustrator, and I sat down right next to each other and put everything together.
Nope. But a great editor (like Donna German) and illustrator (like Susan Detwiler) can make it seem like that's what took place.