Useful code if you don't want your WordPress them to show an update notice.

no_update_theme.php

<?php
/**
 * Keep your theme from updating
 * http://markjaquith.wordpress.com/2009/12/14/excluding-your-plugin-or-theme-from-update-checks/
 */
function s25_no_update_theme( $r, $url ) {
    if ( 0 !== strpos( $url, 'http://api.wordpress.org/themes/update-check' ) )
        return $r; // Not a theme update request. Bail immediately.
    $themes = unserialize( $r['body']['themes'] );
    unset( $themes[ get_option( 'template' ) ] );
    unset( $themes[ get_option( 'stylesheet' ) ] );
    $r['body']['themes'] = serialize( $themes );
    return $r;
}
 
add_filter( 'http_request_args', 's25_no_update_theme', 5, 2 );