I couldn’t find out which pieces of artwork will be displayed, but I hope they include this image of Dorothy and Toto peering at the China Country, viewable through the Library of Congress’s website.
In the large version (click on the thumbnail) one can see how Denslow originally penciled Toto and the Cowardly Lion peering at the china people from the lower right corner. (There are other penciled figures on the left, but they’re hard to make out.)
Denslow eventually chose to draw Dorothy and Toto alone at a larger scale with a thicker line and hatching, to emphasize how she’s much bigger than the china people. And I like how he sat Toto on the internal frame of the picture itself.