A children's book illustrator will design the artwork that help bring an author's story to life. Most children's book illustrators work as freelancers and have contracts with publishing houses.
Most children's book illustrators are self-employed and are hired by book publishers per job. This is because every illustrator has his own style and publishers typically prefer to have different styles for each book they publish. Rather than rely on in-house illustrators, publishers choose freelance illustrators who they think will best suit each book.