Apple has prescribed a certain size of image dependent on the Pass Type.
PassKit automatically scales these images to fit within each allotted space, preserving aspect ratio, but are cropped if the aspect ratio is different than their allotted space.
Please note that your images do not have to be exactly these dimensions, as PassKit will automatically crop, scale and optimise them. However, please check in the Pass Designer that the images appear as you want them to. We also recommend that once you have saved your pass template you test the pass design in both iOS6 device and iOS7 device.
IMPORTANT: If you upload images that are smaller in size than the dimensions above they will not appear sharp. We strongly recommend you do not use small images.