hi,
Showing "Related Products" was problamatic on VM3.x, so we didn't include this feature to CleanMart (yet). The product pictures don't show off.
We are hoping to see; VM Team will fix this problem in the upcoming VM release, (because it is related to core), once this feature starts working just fine with official VM, we will also include it to CleanMart as well.
FYI:
To load the related products on the product page; the code snippet is this:
<?php
echo shopFunctionsF::renderVmSubLayout('customfields',array('product'=>$this->product,'position'=>'related_products','class'=> 'product-related-products','customTitle' => true ));
?>
this snippet should be placed into product details PHP file:
/template/YOUR_TEMPLATE/html/com_virtuemart/productdetails/default.php
Regards.