If so, then replace this:
<a title="<?php echo $ManufacturerName; ?>" rev="iframe|550|650" rel="facebox" href="<?php echo $ManufacturerLink ?>"><img src="<?php echo $product->mf_images[0]->file_url_thumb; ?>" alt="<?php echo $ManufacturerName; ?>" /></a>
with this:
<a title="<?php echo $ManufacturerName; ?>" href="<?php echo JRoute::_('index.php?option=com_virtuemart&view=category&virtuemart_manufacturer_id=' . $product->virtuemart_manufacturer_id.''); ?>"><?php echo $ManufacturerName; ?></a>
So the plain text
<?php echo $ManufacturerName; ?> will be linked, instead of the manufacturer Logo.
Regards.
Support