Here are some screenshots from my Nexus 7. When you tap an image result, a black box with a bigger version of the image will open. You can also find some additional information about the image.
Swipe left to see the next image result, swipe right to go to the previous result. Gestures work just like the left/right keyboard shortcuts in the desktop interface. Tap an image to open the page that includes it.
A similar interface is available for smartphones. Here's a screenshot from an iPhone running iOS7:
Google will probably say that it changed the interface to make it more consistent and provide an unified interface for both desktop and mobile devices. There are some other advantages: you can scroll down to see more results, you can scroll up and quickly change the query or switch to web search.
I find the old interface more intuitive and better suited for mobile devices. It made it more obvious that you can use gestures by showing the previous and the next image result, search results didn't move around and you could find more information about the images. The new smartphone interface only displays the domain name and it no longer shows the title of the page and the image size (the tablet interface still shows them). Here's a screenshot of the old UI:
