This thread is resolved. Here is a description of the problem and solution.
Problem: What is the most efficient way to translate a lot of product images?
Solution: You can use WP All Import & Export, the steps are: - Upload all media - Duplicate the media in all languages from WPML->Settings->Media Translation - Now create a CSV file for default language and secondary language and export it. - Make changes in the CSV file and re-import it.
This is the technical support forum for WPML - the multilingual WordPress plugin.