<li style="background-image:url('<?php if (class_exists('MultiPostThumbnails')) : MultiPostThumbnails::get_post_thumbnail_url(get_post_type(), 'secondary-image'); endif; ?>
?>');"><?php the_post_thumbnail('post-thumbnail', array('alt' => get_the_title(), 'title' => get_the_title())); ?>
<li class="overlay">
