Sometimes in my agent submissions, I’ll see query letters that state that the author doesn’t have an illustrator for their book.
This is okay. In fact, it’s expected!
If an author is not an author-illustrator shopping a book dummy, then the manuscript would be pitched to editors solely as text. Once the manuscript is purchased by a publisher and the edits have been completed, their team (be in the Art Director, Designer, Editor or combination thereof – depending on the house and imprint) will pick an illustrator based on their desired aesthetic and vision for the book.
The author and illustrator are not in communication with each other during the design or illustration process, as the author has done their work (written and finalized the manuscript) and now it’s the illustrator’s turn to fulfill their artistic vision for the story.
So if you’re a picture book author, please don’t worry if you don’t have an illustrator in mind. In fact, it’s best if you don’t. The publisher will have a number of illustrators that they’re looking to work with, and they will be the ones to make that match for you!
(This also means that you don’t have to mention whether you have an illustrator in your query letter!)