You could pull it directly form the database:
global $wpdb;
$random_photo = $wpdb->get_var("SELECT meta_value FROM wp_postmeta WHERE meta_key like 'single_photo' ORDER BY RAND()");
You could pull it directly form the database:
global $wpdb;
$random_photo = $wpdb->get_var("SELECT meta_value FROM wp_postmeta WHERE meta_key like 'single_photo' ORDER BY RAND()");