I have noticed that some sites have an image included on the search listing when googling via a mobile device. To be clear I'm not referring to Google's image index, this is a webpage index that shows the meta description along side an image. It only happens on mobile searches too, not desktop searches.
Having looked at webpages for sites that it's appearing on there doesn't seem to be any logic to it, for example, one site didn't have an og:image tag, so I couldn't put it down to that. One site had a lot of images and the one chosen wasn't the most obvious, i.e. wasn't at the top, wasn't the largest etc. I couldn't see any attributes added to image tags to encourage Google to use it either.
Am I missing something? Is there something I can do to encourage Google to use my logo next to the description text?