If I've understood right...
For product details page:
/customer/main/product.tpl
Code:
{include file="product_thumbnail.tpl" productid=$product.productid image_x=$product.image_x image_y=$product.image_y product=$product.product tmbn_url=$product.tmbn_url id="product_thumbnail" type="P"}
Variables image_x and image_y defines picture's width and height.
Anyway this template (product_thumbnail.tpl) uses for image thumbnail in other templates with same parameters.