I suggest that you don't have child-theme installed. First let's do that:
Child themes
Or you can download the theme from Prasanna web-site (under "download" section)
http://www.prasannasp.net
After that put this code inside of your child theme functions.php file, (if you install child-theme from Prasanna SP site, you already have that file), create one blank file and name it functions.php and upload it to your child-theme folder.
Than insert this code in child-theme functions.php:
<?php
function graphene_homepanes_nolink_img() {
?>
<script type="text/javascript">
jQuery(function($){
$("div.homepage_panes a:has(img)").each(function() { $(this).replaceWith($(this).children()); })
});
</script>
<?php
}
add_action('wp_footer','graphene_homepanes_nolink_img');
?>