Here's an addition to the rationale. Let me know if this is sufficient:
To identify early work by the creator profiled in the encyclopedic article. To identify cartoon collection of the creator profiled in the encyclopedic article. The image is used for identification in the context of critical commentary. It makes a significant contribution to the user's understanding of the article, which could not practically be conveyed by words alone. The image serves as a visual identification of the artist's cartoon work. It illustrates an educational article about the artist, showing his style and technique. Most importantly, it is a self-portrait, and as such it reveals Silverstein's self-image. The Silverstein "travelogue" pages had a unique "sketchpad" format which is not seen here but could be added if necessary.