In order to use an image for a link instead of text, you have to have a way to associate an image with the specific EZ Page you are linking to. The easiest way to do this is to name the image the same as the EZ Page ID. For example, you would name your images 1.gif, 2.gif or 1.jpg, 2.jpg etc. Now that we have a naming convention, all we need to do is replace the text link with some code to insert an image.
Open tpl_ezpages_bar_header.php and find:
<a href="<?php echo $var_linksList[$i]['link']; ?>"><?php echo $var_linksList[$i]['name']; ?></a><?php echo ($i < $n ? EZPAGES_SEPARATOR_HEADER : '') . "\n"; ?>
Replace that with:
<a href="<?php echo $var_linksList[$i]['link']; ?>"><?php echo zen_image($template->get_template_dir($var_linksList[$i]['id'].'.gif', DIR_WS_TEMPLATE, $current_page_base,'images'). '/' . $var_linksList[$i]['id'].'.gif'); ?></a><?php echo ($i < $n ? EZPAGES_SEPARATOR_HEADER : '') . "\n"; ?>
Voilà! Images instead of text for your EZ pages.