Ignore me, once again just after I posted this I was hit by inspiration and worked it out.
If anyone else wants to do it, here is the code for product.tpl:
Code:
{if $product.free_shipping ne "N"}
[img]{$ImagesDir}/free_shipping_small.gif[/img]
{/if}
Here is the code for products_t.tpl:
Code:
{if $products[product].free_shipping ne "N"}
<td width="40%" align="center">[img]{$ImagesDir}/free_shipping_small.gif[/img]
</td>
{/if}
Hope it helps...