our app indicates that it is optimized for the iPhone 6, at least one 4.7-inch screenshot is required. Up to four additional screenshots can be uploaded. You can rearrange the screenshots when you create or edit the iTunes Connect record.
Don’t include the device status bar in your screenshots. Screenshot requirements are:
72 dpi, RGB, flattened, no transparency
High-quality JPEG or PNG image file format
750 x 1334 pixels for hi-res portrait