Last month, Google announced this change on Google Images referral URLs, but at that time, it was not clear how the changes would reflect in Google Analytics.
Previously, all traffic coming from a Google Images search result would be grouped together under ‘google / organic’ in the Acquisition reports in Google Analytics. Soon, when the Google Images team makes their changes to the referral source URL, there will be a new Source line item for image search reflected in Google Analytics which will display as ‘google images’ in the Source report and ‘google images / organic’ in the Source / Medium report within Analytics.
Users will still see a line item for images.google.com in the ‘Referral’ report within Google Analytics. The referral report will continue to show these, and all other sources, as referrals.