I’m not sure if this is an experiment or a feature that’s currently rolled out. Google Image Search for mobile has a new interface that replaces pagination with infinite scrolling, just like the desktop interface. You can see a lot more images without having to swipe and it’s much easier to find great search results. Another difference is that thumbnails no longer have the same size.
Google also added an option to “scroll to top”, but this is more useful if you use Android. iOS has a built-in feature that scrolls to the top of the page (or the current view) when you tap the status bar.
When you select an image result, you’ll probably see a new interface that focuses on the image and makes it more obvious that you can swipe right/left to check to other results. The browser’s address bar is no longer displayed and the image is slightly smaller.
Unfortunately, just like the new desktop image search, the redesigned mobile interface replaces snippets with page titles and removes file sizes (in bytes, not pixels). The most important missing feature is the link to the full-size image. The image is actually loaded in the background and replaces Google’s thumbnail, so you can still long press the image and use browser features that let you save the image or open it in a new tab.
Here’s the old interface:
And here’s a side-by-side comparison (old vs new):