Promomatic helps you easily generate app store assets in various sizes. Simply upload your app screenshots and you're good to go. Thousands of template combinations once you start playing with the customizable device frames, backgrounds, fonts and more!
Making promotional screenshots for the App Store is tedious: it takes time and it's hard for non-designers.
Store Screens is the way to making cool-looking screenshots, for iPhone and iPad without the struggle.
Have a try, it's free :)