Since iOS 7's icons are slightly larger and have a different corner radius, some icons for iOS 6 do not display properly leaving white areas around the edges, notes the report.
In order to avoid this interface issue, developers will need to include larger icons in their applications. iOS 6 icons on the iPhone come in at 114 x 114 pixel resolutions, while iOS 7 icons are slightly larger at 120 x 120 pixel resolutions. For the iPad, iOS 6 icons are at resolutions of 144 x 144, and on iOS 7 they come in at a resolution of 152 x 152:
More specifics on the exact shape and dimensions of the new iOS 7 icons can be found here.