Expressionism in art
Expressionism in film

The Scream (1893), by the Norwegian painter Edward Munch, an important precursor of German Expressionism. Bruno Anthony's mother's portrait of St. Francis (which Bruno mistakes for his father) in Hitchcock's Strangers on a Train.

Expressionism was an art movement associated mainly with German painting and film of the early 20th century, particularly following World War I. Hitchcock, a lifelong art collector, was familiar with German expressionist filmmaking from his work in Germany during the mid-1920s.

The goal of Expressionism was to evoke the subjective responses that the artist has to objects or events. It contrasted with impressionism, which sought to capture the outward impression of an object or scene. And of course Expressionism did not attempt a realistic portrayal of the world.

The stylistic premise of Expressionism was that the artist's response to the environment was so intense that it affected the form of the art. Surface elements are distorted or exaggerated by subjective pressures. As a reflection of the time, Expressionist painting tended to be vivid and violent, with jarring images.
George Grosz, La Ville (1916-17 )
Kathe Kollwitz, Self-Portrait (1923)
George Grosz, Suicide (1916)
Karl Schmidt-Rottluff, Russicher Wald
Expressionism influenced Surrealism, which was also important to Hitchcock's visual sense.

Alberto Martini, Folie, 1914-15
The Surrealist artist Salvador Dali's designs for the dream sequence in Hitchcock's Spellbound.