looking at the source code for you page, I only see the link for the facebook share , i dont see the image tag.
<div class="icons"> <a name="fb_share" type="icon" href="http://www.facebook.com/sharer.ph?u=http%3A%2F%2Fwww.davedeephotos.co.uk%2Fevent.php" title="Facebook"></a>
<script src="http://static.ak.fbcdn.net/connect.php/js/FB.Share" type="text/javascript"></script>
</div>
i created a test page with a face book icon, and mine includes an image tag:
<div class="icons">
<a name="fb_share" type="icon" href="#" onclick="window.open('http://www.facebook.com/sharer.php?u=<?php echo urlencode('http://localhost/uploadprobs/facebooktest.php'); ?>', 'Facebook', 'toolbar=0,status=0,width=626,height=436'); return false;" title="Facebook">
<img src="webassist/social/icons/facebook.png" />
</a>
</div>