"The image of Monk sitting in a little red wagon wearing a suit, sunglasses, and a plaid hat is one of the most memorable in all of jazz. The photograph is credited to Paul Weller and the cover design [to Paul] Bacon, but there is reason to believe that Monk was quite involved in the creation of this image. According to Monk, the original cover design included a photograph of himself in a cowl, standing at a pulpit and holding a glass of liquor. Monk objected to the image for reasons that are not altogether clear, and [Orrin] Keepnews, who was producing the session, agreed to change the cover. Monk claimed that the idea for the final image was his, although, of course, the staging, lighting, and other technical aspects of the photograph are no doubt the work of Weller. In any case, Monk clearly took an interest in the album cover and how it represented him. Perhaps it was a clever rejoinder to critics who had by then made a habit of describing him as childlike, the photo displaying the incongruity of a man, with nothing childish about him, sitting in a child’s wagon. Perhaps it was, as Monk himself claimed, simply an image he liked that represented his intensity: he was so involved with his music that when it struck him, he could compose anywhere, even in his son’s wagon."
Solis, Gabriel. Monk's music: Thelonious Monk and jazz history in the making, University of California Press, Berkeley, 2008.