When the Open Graph - K2 plugin is enabled, JFBConnect will always set the XL image as the og:image tag. If you're seeing a sall image, it could mean a few things:
* The K2 configuration for the XL image size is actually too small
* The K2 configuration option for Open Graph is enabled and set to a smaller size
I hope that helps, but if you're still having issues, try running your page through the Open Graph Debug Tool to see what images are actually being set:
developers.facebook.com/tools/debug
If you need more help from us, let us know a specific URL to a K2 page with the problem.
Thanks,
Alex