ok.. here's an answer for you.. I've been searching EVERYWHERE for this and finally figured it out.. at least how to add to the page to add something for users to click and go to the sites products page.
go to: /components/com_virtuemart/themes/default/templates/pages/shop.cart.tpl.php
On or about line 21 you'll see this code:
<!-- Cart Begins here -->
';
include(PAGEPATH. 'basket.php');
echo $basket_html;
echo '<!-- End Cart --><br />
';
I changed ours to look like this, adding an image as you can see - so make sure you either have the image or change the url to one you do have:
Also note, the link in this code directs them to 'products' which is the page of our vm installation.. change this to whatever your link is.
<!-- Cart Begins here -->
';
include(PAGEPATH. 'basket.php');
echo $basket_html;
if ($cart["idx"] == 0) {
echo '<!-- End Cart --> <br /><br />
<a href="products"><img src="components/com_virtuemart/themes/default/images/back.png" style="vertical-align:text-bottom;">
<span style="font-weight:bold; font-size:18px;">Continue Shopping</span></a>
';
}
If you want to remove the words; "Your cart is currently empty" just remove this:
echo $basket_html;
I you run into any questions let me know, I'll do what I can to help.

J