The shells are all from the 2014 Ukrainian uprising known as the Maidan Revolution, one of the bloodiest European conflicts since the early 1990s.
And the two Ukrainian artists who created the portrait fiercely believe Putin is to blame for the violence that tore apart the eastern part of their country.
"Russia tried to pull us into the USSR," Daniel Green, one of the artists said. "It was a line between democracy or totalitarianism."
Both Green and his fellow artist, Daria Marchenko, took part in the uprising.
Green said several of his friends were killed in the fighting. That's what gave him the idea of using spent bullets to symbolize what was happening.
"I'm ready to die for my country but I'm not ready to kill for my country," Green said. "Culture is a bigger weapon than a machine gun."
He and Marchenko had worked together in the past and decided to create a piece that would draw attention to the horrors of the conflict.
"Daniel is the brain, I'm more fond of optical illusions and making the pieces look unusual," Marchenko said.
The pair started work on Putin's portrait in February 2015. In the beginning, the bullets came from their network of friends who'd taken part in the war. But as word spread, the pair was inundated with remnants from the war. "We had thousands and thousands of shells all over the place," Marchenko said.
"There were splinters of bombs lying in the bathroom, in the kitchen, everywhere."
The artists had been working on the piece for about six months when a friend took a photo of it and posted it on Facebook.
Marchenko said she wasn't yet ready to share the piece with a wide audience. But the reaction to her friend's Facebook post was overwhelming.
Within days, news outlets from around the world descended into their one-room workshop in Ukraine. "We didn't advertise our work at all," Marchenko said. "We were just making honest, nice work with a lot of meaning to the pieces."
Depending on how the light hits the portrait, Putin appears as a menacing presence or a tired, sad man. "Art is based on the question of which kind of character in history this person would like to be. You'll see dictatorship, an iron man or a scared boy," Marchenko said.
"Even dictators, people who make many bad things, they are scared because they will have to answer to heaven sooner or later," she added.
The portrait, known as "The Face of War," is the signature piece of the "Five Elements of War" exhibition at the Ukrainian Institute of America in New York.
Another piece, "The Brain of War" highlights the fine line between truth and propaganda. Two other pieces reflect the "flesh" and "heart" of war. Then there's the installation "Honour," a giant eye that symbolizes the world as mere spectators to the conflict, unwilling to intervene.
"Culture is a weapon of peace," Green said. "We try to show through these images how the domination of war is important in the culture of humanity."
Marchenko added: "We want people all over the world to understand how dictatorship works and the tools of manipulation so they can stand up to it."
The exhibition will run until Feb.4.