Såhär?

 84     public static function get_random() {
 85         $sql = 'SELECT `id` FROM `pics` ORDER BY `id` DESC LIMIT 1';
 86         $result = db::out_query($sql);
 87
 88         $row = $result->fetch_row();
 89         $max_val = $row[0];
 90
 91         $done = 0;
 92
 93         while ($done == 0) {
 94             $id = rand(1, $max_val);
 95             $sql = 'SELECT * FROM `pics` WHERE `id`='.$id;
 96             $result = db::out_query($sql);
 97             $done = $result->num_rows;
 98         }
 99
100         return $result;
101     }