JFBConnect can only generate og:image tags for extensions that an Open Graph plugin has been created for. Currently, we support setting image tags in Joomla Content, K2, JomSocial, EasySocial, Virtuemart, Kunena and some other extensions I'm likely forgetting right now.
Without an Open Graph plugin, there's no good method for JFBConnect to determine the best image from each extension. For title and description, we use the meta data by default, unless there's a better option (like article title, for instance).
I hope that helps explain,
Alex
og:image don't work
