You might be wondering how Facebook choses which thumbnail images to show when someone shares a link on Facebook. It might seem random, but there is a way for you to control which images Facebook uses.
Facebook’s Open Graph allows you to add
<meta> tags to the
<head> section of your site. One of these
<meta> tags is the
og:image tag. It will look something like this:
<meta property='og:image' content='http://www.domain.com/path/to/image.jpg' />
It is possible to add multiple
og:image tags to a page. For each
og:image tag you add, Facebook will add that image to the list of available thumbnails to use each time the page is shared.