Nicki Minaj wanted a cell phone case that matched her larger-than-life look — something cartoonish, with bright colors.

So last year, the pop star turned to Tristan Herbert, a 23-year-old Parkville artist who makes custom covers for iPhones and Androids. Herbert spent 11 hours designing a case with a drawing of Minaj sporting long blonde hair, big hoop earrings, a belly shirt and blazer. The words "Pink Friday," the title of Minaj's first album, run alongside, and the background is, of course, pink. Minaj's people said it was "amazing," and Herbert, then a largely unknown artist, had his first big client.

"Seeing her with the case is amazing," Herbert said. "It's kind of surreal."

Since starting his company, Tristan Art, about eight months ago, Herbert has designed more than 400 cases. His clients include Detroit Lions tight end Brandon Pettigrew, Joe Budden from the reality show "Love & Hip Hop New York," cast members of "Bad Girls Club" and DJ Clue.

Herbert's customers send him pictures of people and faces they want on their cell phone cases, and he illustrates them on his desktop computer. There are few plain white backgrounds — Herbert prefers collages with bursts of color.

"I actually get mad when people ask me, 'Can you just do this and put it on the white case?'" he said. "They don't give me the freedom, really, to do what I want to do."

He hasn't been doing it long. Before he started, he was adrift; he had moved to Baltimore in 2011 to train for soccer, but later realized a torn meniscus would keep him from making a career out of it.

"He wasn't depressed, but he wasn't happy," said his older sister, Nerisha Herbert.

When Herbert's little brother Jamari came to visit him last summer, Tristan asked him, "'What do you see, when you see me?'"

His brother responded, "I just see my big bro."

Jamari didn't see Herbert as someone to look up to — someone he wanted to be like when he grew up, Herbert said, which stung.

"I was like, 'Man, I've got to get it together,'" Herbert said.

Herbert had always been interested in art; he wanted to draw a cartoon series that one day might air on Nickelodeon, he said. Art classes were required at Pendleton High School, in Pendleton, S.C., which he attended, but unlike many of his classmates, he enjoyed them, he said.

Herbert didn't go to college — immediately after high school, he worked for his father in a fabric warehouse, Kravet Fabrics, in South Carolina.

Since he couldn't afford to go to art school, Herbert began to teach himself how to draw cartoons on his computer through trial and error.

"In this eight-month span, I learned what probably would have taken two or three years [in school]," he said.

At first, it wasn't easy going. Herbert admits his early drawings were "horrible."

"I did a picture of Michael Jordan," he said, "and somebody told me they thought it was Shaq."

As he made them, Herbert would post his designs on Instagram, soliciting feedback from others. Soon, people began asking him to draw illustrations. One day in August, Herbert and his brother, Jason, were walking through New York, and Herbert was looking at his Gameboy cell phone case. Staring at his phone, he realized he could add his own designs to cell phone cases.