In another update by Google this week, they have surreptitiously changed the way that traffic from image search is reported. Part way through the month, with no explanation or warning, visits to your site from Google Images are now being reported under the medium of Search Engines, when before they were classed as Referrals.
This update is likely to affect your reporting if you have a number of visits from image searches, so you will need to take this into account when looking at your recent data and making any comparisons.
A working custom segment for image visits prior to the update clearly shows the change:
This was segmented by Medium > Referral AND Referral Path > Matches Regular Expression > ^(/imgres|/images/view|/images/search)
This covered Google, Yahoo and Bing image results. However, now there is not a clear method of segmenting your image traffic from your organic traffic. Not being able to segment this kind of data is going to be quite a bugbear for people, so hopefully a method will become apparent soon.
On the plus side of this change, from an SEO point of view, if you optimise your images then the traffic from these will now be rightfully associated with Search Engines.