Here are the pixel sizes for all device screens. You can use these dimensions as a guideline when using a creative application like Photoshop to create design files.
All assets in App Press are designed for retina displays, and we automatically downsize your graphics to 1x.
iPhone Portrait | width: 640 height: 960
iPhone Landscape | width: 960 height: 640
iPhone 5 Portrait | width: 640 height: 1136
iPhone 5 Landscape | width: 1136 height: 640
iPad Portrait | width: 1536 height: 2048
iPad Landscape | width: 2048 height: 1536
Android Phone Landscape | width: 1066 height: 640
Android Wide Phone Portrait | width: 820 height: 1280
Android Wide Phone Landscape | width: 1280 height: 820
Android Tablet Portrait | width: 1440 height: 2560
Android Tablet Landscape | width: 2560 height: 1440
You can also find this information in the layout editor in the Page Information panel under "Screen Size."