Replace the method get_facebook_photo in the-events-calendar-facebook-importer.php (line 273 in version 1.0.5) to add additional parsing to the Facebook Open Graph picture import.

get_facebook_photo.php

<?php
// use this method to replace the orininal in v1.0.5 (line 273 in the-events-calendar-facebook-importer.php)


/**
 * retrieve a facebook event photo url (after redirect) along with photo data
 * example: https://graph.facebook.com/331218348435/?fields=picture&type=large
 * @param string $object_id the object to retrieve
 * @return array the image url
 */
function get_facebook_photo( $object_id ) {
	$photo_error = false;
	$api_url = $this->build_url_with_access_token( $object_id . '/', array( 'fields' => 'cover', 'return_ssl_resources' => 1 ) );
	$api_request =  $this->json_retrieve( $api_url );
	if( !empty( $api_request->cover->source ) ) {
		$new_path = $api_request->cover->source;
		$get_photo = wp_remote_get( $api_request->cover->source );
	} else {
		$photo_error = true;
	}

	// hat tip to @jessebrede (github) for suggesting a tweak to import old fb image formats if erroring
	if( $photo_error || !empty( $get_photo->errors ) ){
		$api_url = $this->build_url_with_access_token( $object_id . '/', array( 'fields' => 'picture', 'type' => 'large', 'return_ssl_resources' => 1 ) );
		$api_request =  $this->json_retrieve( $api_url );
		$new_path = str_replace("_q.", "_n.", $api_request->picture->data->url );
		$get_photo = wp_remote_get( $new_path );
	}

	// setup return object
	$photo['url'] = $new_path;
	$photo['source'] = $get_photo['body'];

	return apply_filters( 'tribe_fb_get_facebook_photo', $photo, $api_url, $api_request );
}

Should probably look something like this:

function get_facebook_photo( $object_id ) {
$api_url = $this->build_url_with_access_token( $object_id . '/', array( 'fields' => 'cover', 'return_ssl_resources' => 1 ) );
$api_request = $this->json_retrieve( $api_url );
$new_path = $api_request->cover->source;
$get_photo = wp_remote_get( $api_request->cover->source );

    $photo['url'] = $new_path;
    if(is_array($get_photo->errors)){
        $api_url = $this->build_url_with_access_token( $object_id . '/', array( 'fields' => 'picture', 'type' => $size, 'return_ssl_resources' => 1 ) );
        $api_request =  $this->json_retrieve( $api_url );


        $new_path = str_replace("_q.", "_n.", $api_request->picture->data->url);
        $get_photo = wp_remote_get( $new_path );
    }


    $photo['url'] = $new_path;
    $photo['source'] = $get_photo['body'];


    return apply_filters( 'tribe_fb_get_facebook_photo', $photo, $api_url, $api_request );
}

Thanks @jessebrede - have reintegrated the old style lookup so that it pulls both now if needed. This is now integrated in to Facebook Events 1.0.6.