I do different and more flexible.
Just add the following lines into your theme header.php after wp_header();
<script>
var tb_pathToImage = “<?php bloginfo(‘url’); ?>/wp-includes/js/thickbox/loadingAnimation.gif”;
var tb_closeImage = “<?php bloginfo(‘url’); ?>/wp-includes/js/thickbox/tb-close.png”;
</script>
Example:
<?php wp_enqueue_script( ‘jquery’);?>
<?php wp_head(); ?>
<script>
var tb_pathToImage = “<?php bloginfo(‘url’); ?>/wp-includes/js/thickbox/loadingAnimation.gif”;
var tb_closeImage = “<?php bloginfo(‘url’); ?>/wp-includes/js/thickbox/tb-close.png”;
</script>
<body>
Using this, you won’t need to hack your WP core and could keep your installation always fresh. Keep it in mind.
??