<head>
.<meta property="og:title" content="title" />
<meta property="og:description" content="desc" />
<meta property="og:type" content="website" />
<meta property="og:url" content="http://url.com/" />
<meta property="og:image" content="http://url.com/image.jpg" />
og:image
should be at least 200x200, preferably 1500x1500 pixels in size.