First off, this is a great plugin. It works great and offers some excellent upgrades. However I noticed that the on the listing page, the extra images opened perfectly in the thickbox. However i noticed on the listing page, the image marked as the listing thumbnail does not open in thickbox. Looking at the source I found that the class was just "lightbox" and the rel was "thickbox lightbox fancybox".
I went into the plugin files > api > templates-ui.php. The arguments for the listing thumbnail are reversed. On line 373, you switch the rel and class order:
<div class="listing-thumbnail"><a href="%s" rel="%s" class="%s">%s</a></div>
<div class="listing-thumbnail"><a href="%s" class="%s" rel="%s" >%s</a></div>
Alternatively, you could just reverse the arguments by switching the order of Lines 375 and 376.