App icons required

We need some app icons for the iTunes store and the Google Chrome store, together with some banners for the Chrome store, based around an app we are about to launch. Our normal artist wasn't interested, so it gives us the chance to work with someone new. We have a good idea of the basis for this icon, and a screenshot of the software is attached

The Chrome icons are16x16 128x128 pixels and the banners are 920x680, 1400x560 and 440x280 (they may not contain text and must maintain a correct aspect ratio or they will be rejected). A screenshot from the app is attached