JFBConnect doesn't do any resizing or alterations to your images at all. You can check what Facebook sees as your Open Graph tags by running a URL through their Open Graph debug tool, below:
developers.facebook.com/tools/debug
That should show you the actual image it's using from your site.. Facebook may then be cropping it, but we can't prevent that.
This sort of goes along with what I said above... square images are usually the best. Even better is square images with the most important content in the dead center. From that, they can crop horizontally or vertically and hopefully not screw with the intent of the image. They can also use the square directly.
Facebook changes their image handling pretty frequently and there are *a ton* of ways an image can be shown. Obviously, their own guidelines aren't ever perfect.
Hopefully the Debug Tool link above will help shed some light on things and also help you diagnose if it's a wrong image issue (from JFBConnect/Open Graph tags) or something they are doing after the fact.
Keep us posted on if you need anything else,
Alex
Image on FB Newsfeed size is good, on Timeline it is cropped
