British cartoonist Ralph Steadman added his unique and grotesque illustrations to the Rolling Stone issues and to the novel. Steadman had first met Thompson when Scanlan's Monthly hired Steadman to do the illustrations for Thompson's first venture into gonzo journalism called "The Kentucky Derby Is Decadent and Depraved."
Many critics have hailed Steadman's illustrations as another main character of the novel and companion to Thompson's disjointed narrative. The New York Times noted that "Steadman's drawings were stark and crazed and captured Thompson's sensibility, his notion that below the plastic American surface lurked something chaotic and violent. The drawings are the plastic torn away and the people seen as monsters."