In the iTunes connect developer portal for iOS developers, uploading screenshots used to be a matter of putting them in when the app launches – but still having the option to change them later if need be.
But Apple has ended the ability to change or swap out screenshots wants your app is approved. So just like your maiden information you will need to make sure that your screenshots are the ones you want out word facing before you click the ready for App Store approval button.
This will surely come with some grumbles from developers that switched screenshots in and out often to try to attract audiences, but it helps to police the problem of false advertising especially in the gaming categories.