This is great information. To back up one thing you mentioned, 'The publisher will choose and pay the artist', (with luck, one with a track record for sales): as a picture book author in a traditional deal, you will probably have no control over the art-you have to be prepared to let go of preconceived ideas for pictures. At a conference, an art director said she chooses an illustrator who will imagine what no one else would expect from the words. When you write a story about 'Maggie Goes to Her Grandparents', you might imagine your own child going to grandparents as people. But an illustrator could draw them both as dinosaurs or aliens...and it would be a wonderful book. I've had one picture book traditionally published. In it, a crocodile asks a bird to join it for afternoon tea. When writing the story, I imagined a cunning crocodile looking sly, but the illustrator, Nina Rycroft, has depicted it trying to temp the bird with its joyous dancing skills, and has drawn the characters in Fred Astaire and Ginger Rogers poses. And the book is so much better for her and the art director's input. Traditionally published picture books are the work of a team of creatives who will all consider the work 'my book'. ((It was contracted after the manuscript was appraised by a publisher's editor and discussed at a SCBWI conference.))