Apple has informed through a press release that developers can no longer replace images embedded within the description of their own App in the App Store once these have been approved, in fact, the photos will remain the same until the next update.
Beginning January 9, app screenshots will be locked in your iTunes Connect app has been eleven approved. New screenshots may be uploaded When You submit a binary for an update to an existing app or a new app. For more information on capturing and using screenshots, read the Xcode User Guide.
This is still a drawback for developers since they had the ability to change the screenshots eventually if a fault or flaw detected in it, and if they wanted to highlight a particular function or feature. Apple notes that if you can add new screenshots when submit a binary for an update of the application, is the only way.