Another issue, but also there: PNG images above a certain height failed to load on the iPhone 4. We were facing that problem with our mobile testing tool. Converting the images to JPG solved the problem.
> JPEG images can be up to 32 megapixels due to subsampling, which allows JPEG images to decode to a size that has one sixteenth the number of pixels. JPEG images larger than 2 megapixels are subsampled—that is, decoded to a reduced size. JPEG subsampling allows the user to view images from the latest digital cameras.
Reference: https://developer.apple.com/library/IOs/#documentation/Apple...