Hey guys I have updated our plugin with a change to retrieve cover images instead of the normal picture api. In the next release it will have this built in; however, in the meantime if you feel like replace the method get_facebook_photo in the-events-calendar-facebook-importer.php (line 273 in version 1.5) to add additional parsing to the Facebook Open Graph picture import. You can use the code in https://gist.github.com/codearachnid/5371606 to get the largest version of the cover image that Facebook will supply.