last viewed posts plugin & Custum field, how to?

Hi,
i’m happy to this unique plugin, and i want to do some change i need, so i’d like to knwo how can add this code:

<?php if ( $var_img01 ) { ?>
<a href="#"><img src="<?php echo $var_img01; ?>"/></a>
<?php } else { ?><img src="#/img/no-img.jpg"/>
<?php } ?>

to work with it function:

<?php if (function_exists('zg_recently_viewed')): if (isset($_COOKIE["WP-LastViewedPosts"])) { ?>
<h2>Last viewed posts</h2>
<?php zg_recently_viewed(); ?>
<?php } endif; ?>

Thanks.