I couldn't find an answer, either, so I decided to experiment a bit and came up with the following code to make it work. Bear in mind I am using 1.1.7, but this ought to work on 1.1.3, as well.
The file you want to edit is:
websitename.com/components/com_virtuemart/themes/[virtuemart theme]/templates/order_emails/confirmation_email.tpl.php
("websitename.com" is, obviously, the name of your website. [virtuemart theme] is the current theme you have setup for VIRTUEMART, which you configure in the administrator backend of the website).
First, scroll down to about line 159 where you see a bunch of table cells. Right under where you see:
<th><?php echo $VM_LANG->_('PHPSHOP_CART_QUANTITY') ?></th>
Make a new line that is simply:
<th> </th>
This will be an empty cell as a placeholder so everything is still in order once we insert our pictures.
After this, go to about line 182 (more or less). Here you will see:
<td><?php echo $my_qty ?></td>
Make a new line under this and insert the following code:
<td><img src="websitename.com/components/com_virtuemart/shop_image/product/<?php echo $dboi->p("product_thumb_image") ?>" alt="noimage" border="0" /></td>
Insert the edited file back into your website and test it out. Let me know how it works for you! Once again, I am on 1.1.7, so the code might be a little different.