A picture book for children essentially provides the child with a visual experience. A picture book is any book that contains illustration in which tells a complete story. They may be long narratives or completely wordless. The pictures may stand alone in it's details to complement the text or it may enhance and add detail to the text. In any event, the pictures are part of the story. So when reading this type of book, pause and look. It is after all, the visual experience, that makes this type of book unique in the publishing world.
Picture books in all their varied formats include some fun illustrations that you may not have thought of. One such category are books that use text as illustrations. Concrete poems which take the shape of the object they describe are one example. For a fantastic example of this check out Chris Raschka's A Poke in the Eye. Each poem is a work of art which Raschka embellishes with collage.
Another great book that featured this concept was Bembo's Zoo which is out of print. Each of the letters of the alphabet were used to create an animal that corresponded with that letter. You can still see this artwork on the web at http://www.bemboszoo.com/
Michele, Children's Librarian