Only recently, Google has introduced some changes in the Google Images referral URLs. Thanks to these changes Google Images data are now showing in Google Analytics as a separate data source. This gives you a valuable source of information to help you better understand the traffic coming to your website.
As Krista Seiden, Google Analytics advocate explains in her article, originally, all traffic coming from Google Images search was listed under ‘google / organic’ group in the Acquisition reports. Newly this data has a separate line and can be found as ‘Google Images’ source and in the Source / Medium report as ‘Google Images / organic’.