La guerre, ou La chevauchée de la discorde

La guerre, ou La chevauchée de la discorde (“War, or the Ride of Discord”) — Henri Rousseau, 1894

Ah, this guy. A self-taught artist who only started seriously painting at age 40 and quit his job at age 49 to paint full-time, he definitely had a style of his own. His contemporaries (both critics and other artists) mostly made fun of him, but he did gain a small following, and folks like Picasso, Sylvia Plath, and the Surrealists later praised him as an avant-garde genius.