There is a new form of images being tested in mobile search results in Google. Similar images were being tested back in December 2014, but in this test, the images look slightly larger and are placed on the left side of the snippet.
Below is an image by Bryan P. Hammond (sent in to Search Engine Land). In the image, it shows the title, URL and in the snippet area, you’ll see the description on the right and the image on the left.
Although images could very likely slow down the search results page, Google always tries to strike a balance between making the search results load as quickly as possible, regardless of if you’re using the mobile platform, or desktop. But with these images, it can give the searcher as much information as possible before clicking on the search result.