I knew you would be needing some more customization, but was too tired to concentrate on it last night:) Since you will need to edit a file anyway, your best bet is to insert the image link directly rather than modify the featured functionality. I suggest adding to /includes/templates/your_template/templates/tpl_index_default.php, just before the "</div>" line at the bottom:
PHP Code:
<?php
$show_display_category->MoveNext();
} // !EOF
?>
</div>
Add a new div something like this:
PHP Code:
<div id="featuredLink">
<?php echo '<a href="' . HTTP_SERVER . DIR_WS_CATALOG . 'your_link_path">' . zen_image($template->get_template_dir('your_link_image.jpg', DIR_WS_TEMPLATE, $current_page_base,'images'). '/' . 'your_link_image.jpg', 'Your Link Alt Text') . '</a>'; ?>
</div>
End result:
PHP Code:
<?php
$show_display_category->MoveNext();
} // !EOF
?>
<div id="featuredLink">
<?php echo '<a href="' . HTTP_SERVER . DIR_WS_CATALOG . 'your_link_path">' . zen_image($template->get_template_dir('your_link_image.jpg', DIR_WS_TEMPLATE, $current_page_base,'images'). '/' . 'your_link_image.jpg', 'Your Link Alt Text') . '</a>'; ?>
</div>
</div>
Substitute the correct values for your_xxx, but keep quotes where they exist.
Save the image in /includes/templates/your_template/images/.
Style #featuredLink similar to #featuredProducts, though it will be simpler.