A member in the WebmasterWorld forums pointed out Google Image search is testing a new search results preview layout.
I was able to replicate the test in Google Image Search Germany on Chrome.
Typically what you see when you click on an image from within Google Image search is a preview of the image and the page on the left hand side and some image information and links on the right hand side.
But what Google is testing in Germany is a new top frame method, which seems to be the old way Google handled these images.
Here are screen shots to clarify what Google is testing.
Google Image Result Now:
Google Image Result Test in Germany:
The member also explained the difference in the click action, saying:
I was surprised when I clicked a thumbnail. The picture is not shown in an iFrame as in the .com-imagesearch. The source-website is loaded directly.
Forum discussion at WebmasterWorld.