function erics_random_header_image() {
    echo '<img src="';
    echo  bloginfo('template_directory');
    echo  '/images/';
    $number = rand(1,3);
    switch ($number){
            case 1:
                    echo 'game-pac-man.jpg';
                    break;
            case 2:
                    echo 'game-robotron.jpg';
                    break;
            case 3:
                    echo 'game-atari-space-invaders.jpg';
                    break;
    }
    echo '">';
}