Show random image in the infowindow message on the google maps

gistfile1.txt

add_filter('wpgmp_featured_image', 'wpgmp_featured_image',1,3 );

function wpgmp_featured_image($image,$post_id,$map_id) {
	
  	// Modify img tag containing featured image.

  	$image = '<img src="http://lorempixel.com/400/200/" />';
	return $image;
}