For about a decade, people in the New York art and fashion scene have relied on Eric Wrenn, an unassuming designer known for his minimalist touch, to help shape the images of their brands.

Mr. Wrenn, 38, has worked on ad campaigns, logos, books, websites, stationery, business cards and invitations to runway shows. Through it all he has kept a low profile, but his client list reads like a who’s who of downtown bluechips.

“Eric feels like an industry secret,” said Emily Bode Aujla, the designer and founder of the brand Bode.

“He has an art-world sensibility, and talking with him about a project can feel more like a therapy session,” she continued. “I lean on Eric to help me conceptualize Bode’s entire brand identity. When I hear a brand is working with him, it’s like: ‘Oh, they know.’”