Remove and replace twentyeleven headers

// Remove the default headers
function nomnom_remove_twenty_ten_headers(){
    unregister_default_headers( array(
        'wheel',
        'shore',
        'trolley',
        'pine-cone',
        'chessboard',
        'lanterns',
        'willow',
        'hanoi')
        );
}
add_action( 'after_setup_theme', 'nomnom_remove_twenty_ten_headers', 11 );

// set our own default header image.
    define('HEADER_IMAGE', get_stylesheet_directory_uri() . '/images/headers/wheel.jpg');

// Add our own custom headers packaged with the child theme. in the child theme template directory 'images/headers/'
    register_default_headers( nomnom_theme_headers() );
/* Build the Header Array from the theme headers */
// No need to code the headers just loop through the folder and return a list
function nomnom_theme_headers() {
    global $themename;
    $list = array();
    $imagepath = STYLESHEETPATH .'/images/headers/';
    $imageurl = get_stylesheet_directory_uri();
    $dir_handle = @opendir($imagepath) or die("Unable to open $path");
    while($file = readdir($dir_handle)){
        if($file == "." || $file == ".."){continue;}
        $filename = explode(".",$file);
        $cnt = count($filename); $cnt--; $ext = $filename[$cnt];
        if(strtolower($ext) == ('png' || 'jpg')){
          if (!strpos($file, '-thumbnail') > 0) {
                $header = array(
                    'url' => $imageurl .'/images/headers/' .$file,
                    'thumbnail_url' => $imageurl .'/images/headers/' .$filename[0] .'-thumbnail.' .$ext,
                    'description' => __( $filename[0], $themename )
                );
                array_push($list, $header);
          }
        }
    }
    return $list;
}