Facebook displays three thumbnail images when setting just one image in the Facebook og meta tag:
<meta property="og:title" content="Keystone Business Products - Allentown, Reading, Scranton Copiers"/>
<meta property="og:image" content="http://www.keystonebp.com/img/quote.jpg"/>
<meta property="og:url" content="http://www.keystonebp.com/"/>
<meta property="og:type" content="website"/>
<meta property="og:description" content="Are you looking for a copier in the Allentown, Bethlehem, Scranton, or Reading areas? Read more about the family owned local dealership you can trust."/>
The first thumbnail image is the one I have set as the og:image. The other two thumbnail images are images displayed in the body of the page.
The og image is 256x256 pixels. My website is using PHP5. The og:title, url, type, and description tags are all being displayed correctly. The facebook debugger shows no warnings.
I'm not sure what else to say... I'm using a boilerplate template, the bizstrap corporate template. The images being pulled are from a slider in the middle of the page. Feel free to take a look at my website:
I've found this question two other times on the board but neither one has an answer...
og:image
tag on that page . the debug tool shows that, and calling your script in the browser and viewing source code as well. – CBroe