Hi Xavier,
I found it myself, and it works !
Thanks again for the inspiration, just what I needed.
For eveybody who would like to achieve the same, this is the original code in the listing_table view :
<div style="height:<?php echo $divHeight;?>px;text-align:center;clear:both;" class="hikashop_product_image">
<div style="position:relative;text-align:center;clear:both;width:<?php echo $divWidth;?>px;margin: auto;" class="hikashop_product_image_subdiv">
And this is what I made of it :
<div style="height:100px;text-align:center;clear:both;" class="hikashop_product_image">
<div style="position:relative;text-align:center;clear:both;width:100px;margin: auto;" class="hikashop_product_image_subdiv">
Nico