Google's been in the process of revamping some of the visual style, rather the UI, of the mobile search page for the web as well as the image search pages, and it appears that Google may be ready to finish off the rollout of the new look. This is the same set of changes people have been seeing in the test for this new UI since earlier on in the year but now the difference is that the test seems to be over with Google pushing out these subtle visual changes to a majority of users if not all users. Having said that, most people should be able to open up Chrome on their Android smartphone or tablet and see the touched up UI when they tap the images link.
Things are a little more noticeable if you actually search for images, so give it a shot and see if you can spot the tweaks Google has made here. You should be able to see things pretty quickly, as Google's taking more of a focus to presenting users with image search results that include larger images, drawing more of the user's attention to the pictures. When tapping on an image users should notice that the background behind the image has also been switched from a black background color to a light gray.
Other than the subtle visual updates, Google is making it easier to find "like" image as well with a new related images section. So let's say you're searching Google Images on your smartphone for "Tokyo Street Art." After the image results pop up, you can scroll through vertically to find the images you want to take a closer look at, and when tapping on them you'll see the new backgroundf color, but scrolling a bit down also reveals a new set of images related to the one you're already viewing. You can also see a bar on the main images search results page after searching for an image topic which has links to related image searches similar to the one you initially searched for. These aren't major changes here, but they certainly help to make the overall experience of searching images on mobile a more enjoyable experience.