OK, in this case you mod will work as follows:
0) The product's table is rendered according to the skins/admin/en/order/invoice/parts/items/items.tpl template. Of course, I am talking about admin area right now, but let's solve the problem for invoice in admin area first, so you could get an idea of approach and then you will be able to simply re-apply change to mail notifications.
1) You need to insert a template that will define a new column of the table into the "invoice.items.head" view list. The process is described here:
http://kb.x-cart.com/display/XDD/Step+2+-+applying+design+changes#Step2-applyingdesignchanges-Addingnewtemplatesandwidgets
The code of such template will be something really easy like:
Code:
{* vim: set ts=2 sw=2 sts=2 et: *}
{**
* @ListChild (list="invoice.items.head", weight="5")
*}
<th class="item">Image</th>
2) Then, you need to insert a template into "invoice.item" view list. This template code will be simple as well:
Code:
{* vim: set ts=2 sw=2 sts=2 et: *}
{**
* @ListChild (list="invoice.item", weight="5")
*}
<th class="item"><widget class="\XLite\View\Image" image="{item.getImage()}"
alt="{item.getName()}" maxWidth="80" maxHeight="80" /></th>
Please, let me know if it makes sense to you.