The Google Operating System reports Google is testing a new Image Search interface for related searches.
The example given shows images for [nexus 7], At the top is a carousel of related searches to the [nexus 7]. When you click on one of those related images, Google will show you a larger thumbnail image of the images that match that related search within the black preview window.
Below are screen shots from Alex Chitu:
Then, click on a related search phrase: