When people submit stories from your blog on to social sites like Digg or Facebook, they also have to choose a thumbnail image that should go along with that link. These thumbnails are often generated automatically from pictures that are found in the corresponding web page or blog post.
Giving choice to the story submitter is good but can sometimes lead to irrelevant or even humorous choice of thumbnails. To prevent this, you can actually decide (or force) the exact thumbnail image that should be displayed next to your stories that either shared on Digg or Facebook.
To put your choice of thumbnail, simply to include an additional <link> tag in the <head> portion of your blog template that points to the URL of the appropriate thumbnail image as shown here.
<meta name="title" content="Digital Inspiration" /> <meta name="description" content="Technology and Software Blog" /> <link rel="image_src" href="http://www.labnol.org/screenshot.png" />
You may already have the <meta> description tag in your blog template but make sure that you also add the <meta> title tag for blog thumbnails to work. The <meta> title can have the same value as the actual <title> tag of your web pages.
Google and Blog Thumbnails
Steve Rubel earlier discovered that Google displayed thumbnail images next to search results that pointed to WordPress blogs.
That experiment was for a short period but there’s a possibility that, in future, Google (and other search engines) could use the URL sharing standard discussed above to discover thumbnails associated with a particular blog post and display them in search results.