While Sub Rosa's name may be indicative of the shop's conversations with clients, which CEO Michael Ventura says are kept strategic, personal and quiet, it's certainly not an apt way to describe the work the New York shop does.

Among its more notable campaigns was "For Women by Women" for General Electric, a design installation that sought to change the mammography and breast-cancer experience. "It's simultaneously exhilarating and real, exactly the type of project we look for," said Mr. Ventura.

The 21-person agency surpassed $10 million in billings this year and boasts clients including Nike and General Electric. It has had 200% year-over-year growth since 2009, and expects to see that trajectory continue into 2013, with work rolling out for Nike that aims to change the athletic brand's retail strategy globally.

"We are now being asked to both advise on work and execute it, in an industry where shops usually do one or the other," said Mr. Ventura. That means that the agency tries to hire people who might be excellent at one thing, but have aptitude for five or six other things as well.

"Sub Rosa combines tremendous creativity and strategy with flawless execution," said Linda Boff, executive director of global, digital, advertising and design at GE. "Lots of agencies have ideas; very few are able to actualize those ideas."