Google seems to be testing yet another feature to show image thumbnails in the refinement bubbles/buttons at the top of your Google Image Searches. The refinement buttons let you further filter your image search to specific categories and here Google is testing to see if adding thumbnail images help.

Here is a screen shot from Chinchu KB on Twitter:

Here is what I see:

I currently cannot replicate this on desktop or mobile, but it wouldn’t surprise me if Google is rolling this out now based on comments made in this CNBC article about a search quality meeting inside of Google.

Forum discussion at Twitter.