User:Goetzkluge  

Left: Henry Holiday's depiction of the Baker's uncle (in Lewis Carroll's The Hunting of the Snark, 1876) with some of the Baker's 42 boxes outside of the window.
Right top: John Everett Milais: Christ in the House of his Parents (aka The Carpenter's Shop, 1850, Pre-Raphaelite) with a flock of sheep outside of the window symbolizing the the laity).
Right bottom: Edward VI and the Pope: An Allegory of Reformation (mirrored view, 16^th century) with a violence scene of the reformation depicted outside of the window.

I think, Millais quoted from the 16^th century painting: The red flower in Millais' window corresponds to a mutilated body visible through window in the 16^th century painting. And Holiday (who perhaps understood Millais' quotes) quoted from Millais' painting as well as from the 16^th century painting.