FiftyThree, the software development team behind Paper, the highest-grossing app in the iTunes store, has raised $15 million in investment funding to create what it thinks of as the Office suite of a more creative future, reports The Verge.

“Our goal is to build essentially a suite of mobile tools for creativity,” says FiftyThree founder and Microsoft vet Georg Petschnigg, which means for all intents and purposes, FiftyThree has just begun. Well, Microsoft just debuted Office for iPhone, but an app that defined productivity on desktops — ported to mobile — doesn’t seem to be what Petschnigg has in mind. “It’s about imagining the right solution,” he says, “and that takes time.” … 

Paper, awarded the title of App of the Year in 2012, works on the freemium model: the app is free, and you then buy paintbrushes for $2 each. It has seen 8 million downloads, 1.5m of them in the first two weeks. The app was updated last month with new features, including Made with Paper, a social feed of other people’s work created with the app to provide inspiration.

FiftyThree isn’t giving much away when it comes to its future plans.

Petschnigg has quietly amassed an all-star team of hardware designers for an undisclosed project. The company was co-founded by John Ikeda, who designed every Xbox 360 accessory from the controller to the Kinect, and has hired Jim Koo, ex-director of mechanical engineering at Sonos, and Audrey Louchart, who designed Microsoft’s award-winning Arc Mouse.

Given its track-record and the caliber of its team, however, we’ll be watching with interest.