[martingordon]

I was under the impression that not specifying a device modifier would allow the image to be used on both devices. From Apple's documentation:

Applications running in iOS 4 should now include two separate files for each image resource. One file provides a standard-resolution version of a given image, and the second provides a high-resolution version of the same image. The naming conventions for each pair of image files is as follows:

Standard: <ImageName><device_modifier>.<filename_extension> High resolution: <ImageName>@2x<device_modifier>.<filename_extension> The <ImageName> and <filename_extension> portions of each name specify the usual name and extension for the file. The <device_modifier> portion is optional and contains either the string ~ipad or ~iphone. You include one of these modifiers when you want to specify different versions of an image for iPad and iPhone. The inclusion of the @2x modifier for the high-resolution image is new and lets the system know that the image is the high-resolution variant of the standard image.

That said, it would be cool if Apple produced four different variants of an app and would send you the proper one depending on the device you download it on. When downloading with iTunes, your machine would download and store all four versions.