Neiman served in the U.S. Army during World War II. He worked as a cook until the end of the war, when his art skills were recognized and put to use painting sets for Red Cross shows. Following his return in 1946, Neiman studied briefly at the St. Paul School of Art, then at the School of The Art Institute of Chicago on the G.I. Bill. After graduating, Neiman served on the Art Institute faculty for ten years. During the time Neiman was teaching, he was exhibiting art in competitions and winning prizes. In 1954, Neiman began his association with "Playboy" magazine. Neiman had met Hugh Hefner while doing freelance fashion illustration for the Carson Pirie Scott department store chain, where Hefner was a writer. Hefner and "Playboy" art director Art Paul commissioned an illustration for the magazine's fifth edition. Hefner told "Sports Illustrated", "I don't remember the moment. Our eyes did not meet across a crowded room." One day, after Hefner had started his magazine, he ran into Neiman on a street and asked him to become a contributor to "Playboy". Among Neiman's contributions over the next 50 years, he created the Femlin character for the Party Jokes page, and did a feature for 15 years titled "Man at His Leisure", where Neiman would paint illustrations of his travels to exotic locations.