Specify image to use for facebook thumbnail

Hi and thank you for this great plugin. I’m having trouble figuring out how to select a thumbnail image to go with posts I share on FB. The featured image is always selected (good) but facebook crops the photo sometimes to fit their specs (bad). Is there a way to have a featured image to use elsewhere on my site and also a facebook thumbnail image that I identify to display with shared posts? Thanks!

http://wordpress.org/plugins/wp-open-graph/