There was a time — say, from the rise of Grandmaster Flash in the 1970s to the fall of the 42nd Street grindhouse in the ’90s — when a singular trend in portrait photography took root in New York, from Times Square to Harlem to Coney Island. Street photographers, usually wielding Polaroid cameras, set up backdrops airbrushed onto bedsheets, hung those sheets from the gates of shuttered storefronts and invited passers-by to pose in front of them in exchange for small donations.

The backdrops, to exercise the imagination slightly, were an urban version of medieval unicorn tapestries, evoking icons like gleaming BMW’s or wads of $1,000 bills accompanied by slogans like “Living Large” or “I Wanna Sex You Up.” For the photographers who used them, like Louis Mendes (“Shaft with a camera,” a Facebook fan once called him), the backdrops were an easy way to make a little “coffee money,” as he put it. For the clientele, they were both souvenirs from a night on the town and pictorial proof of personality. That painted Tweety bird? That’s so me, man; that’s what I’m about.

The phenomenon died more or less with the Disneyfication of Times Square. Many of the backdrops were seized by the police and eventually sold at auction, and the whole idea seems quaint today in a world of digital clip art. “With the Polaroid, people couldn’t wait for it to come out,” said one photographer, Mike Holmes. “There was excitement and exuberance.” As Mr. Holmes added, however: “The city’s changed. It’s a different world here now.”