The image tag is in the /components/com_jfbconnect/libraries/provider.php file. Around line 237, you'll see:
return '<div class="' . $loginClass . ' pull-' . $alignment . '"><a' . $display . ' id="' . $loginId . '" href="javascript:void(0)" onclick="jfbc.login.provider(\'' . $this->systemName . '\');"><img src="' . $buttonImage . '" alt="' . $buttonAltTitle . '" title="' . $buttonAltTitle . '"/></a></div>';
Hopefully that helps with what you're looking for, but if you were looking for something else, just let me know.
Thanks,
Alex
specify images dimensions
