The original artwork is in the archives of the International Wizard of Oz Club. The piece appears to have had a rough life, but this is because it originally served two purposes. The main drawing of the Scarecrow and Tin Man was done to be used as endpapers in the Little Wizard series of books. There was no landscape in the background, just a shadow under each of the figures. The image was printed in blue ink, and the shadow was stippled rather than solid.
In 1932, some of the Little Wizard books were reprinted to be used with sets of jigsaw puzzles, and later as advertising for Jello; this time the image was printed in black with solid shadows underneath. This seems to be what the original artwork would have looked like in its original form.
When looking at the drawing in the club archives, it becomes obvious that the main image of the characters was drawn on a smaller piece of paper, which was later glued to a larger sheet. The shadows beneath the figures were whited out, and a new background was drawn in by John R. Neill. Several of the illustrations from the Little Wizard Series were adjusted and reused in The Patchwork Girl; in this case, the paper size needed to be increased in order to be the correct proportion for the larger book!