Change image that appears in Google mobile results?

I noticed sometimes when I search a term on my phone, an image will appear next to the listing. In the case of products this is usually the product image. In the case of homepages appearing in search results, the image seems to be chosen at random. I would think in the case of a WordPress site it would default to the featured image of the homepage.

How does Magento decide what image to give to Google? Is it completely at random? Is there anyway to control this?

I use MageWorx SEO suite and don’t recall anything in the settings controlling this. Basically the image that appears is skewed so I would like to know what image size is most appropriate and how I can control what image appears?