I think that you could use a picture of an abandoned bus, a grain elevator, a book by Henry David Thoreau and Jack London, Devil's Thumb, a journal, and berries. All of these relate directly to the character of Christopher Candless.
Each item speaks to the kind of person that he was ending with the van. What you could do is create a time-line of his life using images as they were brought up in the novel in chronological order. This would create a picture book relating each of the images to the movement of Candless' life as depicted in the novel.