plugin: thumbnail for posts on facebook

I was wondering if something like this exists for Elgg:

On facebook, I want to post a link to public content on my Elgg site.  When I do, and it is a link to a photo, or an image file, or a video, no thumbnail appears on facebook.

The goal is to draw people away from Facebook to Elgg.  A plugin like the Wordpress one above would help with the goal.  At least, people would be more inclined to go to the site if they saw an interesting thumbnail, and possibly comment via another elgg plugin called facebook connect.

ps.  I was looking for a way to turn off comments on Facebook, but there is none.  I will have to put a message each time telling people not to comment on Facebook (instead on elgg site), as I will delete each comment!  Ha!