FACBOOK og:image siez

The XS size is meant to be small, it's eXtra Small. I'm assuming you're using K2. If so, and you have the Open Graph - K2 plugin installed/enabled, JFBConnect should try to use the XL image, if available. That should be the right image for Facebook and not need any extra work on your part.

Hopefully you found a solution that works for you, but if you need anything else, just let us know.

Thanks,
Alex