An artist friend of mine pointed me towards this Aristide Bruant
anecdote, saying it was very Under the Poppy-esque:

Bruant always greeted everyone who entered his cabaret with curses, but he admired Lautrec, and when he arrived, Bruant would roar, “Silence, gentlemen, here comes the great painter, Toulouse-Lautrec, with one of his friends and a pimp I don’t know.”
[from Frokje Hoekstra's Henri de Toulouse-Lautrec]

My friend also insists that Toulouse-Lautrec would be the go-to guy for the book’s cover art. Which set me dreaming. . .