Thank you for contacting WPML support. While you are waiting for one of my colleagues to take this ticket and work on it, let me provide you with the first debugging steps and try to help with the issue quickly.
You need to use a WPML media addon and add different images for your 2nd language.
Another way would be using manual translation and changing settings for media custom fields, but this is not the recommended way, and not sure what can go wrong.