For whatever reason, PP Pro doesn't fire the necessary hooks to make things like vBSEO work in the Gallery section of a site, so Analytics doesn't get added as it does on all other pages of a vBSEO-powered site.

A workaround for vBulletin 4 -

In ad_header_end template, insert the following code, replacing the bold bit with your Analytics account number.

Code:
<vb:if condition="PP_SCRIPT == 'PP_Pro'">
<vb:literal><script type="text/javascript">

  var _gaq = _gaq || [];
  _gaq.push(['_setAccount', 'UA-XXXXXX-1']);
  _gaq.push(['_trackPageview']);

  (function() {
    var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
    ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
    (document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(ga);
  })();

</script></vb:literal></vb:if>