This comment came in from Priscilla via the blog:
I have heard that an author/illustrator needs to first “prove herself” as an author or an illustrator before being published as an author/illustrator. Is this the case? What is your advice for an author/illustrator on submitting a picture book when the text and images are dependent upon one another for meaning? As the Andrea Brown Literary Agency does not accept attachments with queries, a mock-up or dummy would be out of the question. But would an agent be interested in receiving written illustration ideas alongside a text query, or should the illustrations come later, only after an agent expresses interest in the project?