[B00MER]

skin1/modules/Detailed_Product_images/product_images.tpl update this file with the following code.

{if $images[image].tmbn_url}
[img]{$images[image].tmbn_url}[/img]
{else}
[img]{$xcart_web_dir}/product_image.php?imageid={$images[image].imageid}[/img]
{/if}