Just a guess that these pictures are from job assignments.  They were together mostly in a portfolio  in which some of the work was clearly commercial.  I eliminated about 50 that were unsigned as they may not be Bill’s.  For example,  I found a an illustration by Boris Artzybasheff of a fox and goose (not included) followed by Bill’s illustration of a fox (included).

Seems like personal and business work were mingled on occasion. Here are  two examples.  Business work on left.

The rest …