Visual Social Marketing: How to Choose an Image to Accompany a Link on Facebook
After you have included a link to a web page in a social marketing status update, Facebook makes it more visually appealing by automatically searches the web page for images to accompany the link that's shared. This statement is true whether you're sharing content from your own website or from any other website. After a link is included in a status update, Facebook searches the site for images.
You may scroll through the image choices to accompany a link by pressing the arrow buttons below the initial image. In this way, Facebook lets users select the image to accompany the post.
If you still don't find a relevant and engaging image, Facebook also lets you upload your own thumbnail image to accompany the post. For example, if you’re sharing a newspaper article that doesn't have a photo, but you still want to optimize the post, you can upload a relevant photo from your computer.
Optimize your website images for Facebook. Though uploading your own photo can help you create an optimized image for the Facebook newsfeed, when an article has no images, other people who are sharing your website, product pages, or blog posts probably won't take the time to upload their own image.
To determine the images that users can choose from when sharing your site, create a status update with a link to your website, and note the images that Facebook allows you to choose from.
You may notice that Facebook doesn't recognize all the images on your page, or that it defaults to an image that isn't at the top of the page. Facebook chooses the images to be displayed based on how your website is coded, and how the images are coded and labeled.
After you enter a URL, Facebook shows you any coding errors on your site and displays the images that it recognizes from your website. It's another way to find out whether your images are coded correctly in order to be recognized by Facebook.