I did check it in Firebug but didn't see anything that I might change to make a difference.
<div class="thumbnail " style="background-image: url("http://ejmgroup.com/wp-content/images/projects/frontpg_banner/ejm_ftpg_01.jpg");
background-position: center center; background-repeat: no-repeat; margin-left: 40px; width: 210px; height: 90px; visibility: visible; opacity: 0.5;"></div>
It looks at though only the center 210 by 90px of the image are displayed rather that the image shrinking to fit within the 210 x 90px.
A link is here, but I see this happening in every gallery that I have posted. http://ejmgroup.com/index.php