I have this working in 2 separate areas of my product.tpl. Below is an example and you can see more at:
http://forum.x-cart.com/showthread.php?t=25143 (post #20 - #26).
example:
{section name=field loop=$extra_fields}
<div id="download">{if $extra_fields[field].service_name eq "products_PDF" && $extra_fields[field].field_value ne ""}{include file="modules/Extra_Fields/document_icon.tpl"}
{/if}</div>
<div id="download">{if $extra_fields[field].service_name eq "products_manual" && $extra_fields[field].field_value ne ""}{include file="modules/Extra_Fields/document_icon.tpl"}
{/if}</div>
{/section}
I also have this working within our tabs.
Christine