Your App Icon is one of the best marketing tools in your arsenal. Testing your icons and getting social proof is one of the most important things you can do for your new app. People who are seeing your icon are viewing it on their devices so it’s critical you see how they will look opposed the a larger version with our Icon test. Upload your new App Icon to see how it looks!
Preview Your Icon on the iPhone and iPad
Share with your Social Networks
Download All your icons in all the sizes, nice!
There are many great resources online regarding great icon design, you can check Gizmodo Article on App Icon Design here as a good place for the basics.