Having upgraded to 4.4 needed to make it work for that version.
None of our images are held in the database, they are all files.
Here is what I did.
in skin/common_files/mail/html/send2friend.tpl
added the following line above {$product.descr}<br />
{include file="stf_product_thumbnail.tpl" productid=$product.productid product=$product.product}</a>
Then in skin/common_files/ created a file called
stf_product_thumbnail.tpl
containing;
{*
$Id: stf_product_thumbnail.tpl,v 1.0 2011/06/29 08:57:58 joy Exp $vim: set ts=2 sw=2 sts=2 et:
*}
{strip}
<img src="{$http_location}/image.php?id={$productid}" width="150">
{/strip}
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Have just done this on 4.5 and it works perfectly for me. You can test it on the site.