I have the Send to a Friend add on. My Email does not contain an image - only a URL. I have not checked its functionality in some time but I do remember it having that Capability at one time.
Joomla: 3.7.3
JoomShopping: 4.15.1
Website Url: www.wildbikers.com
JoomShopping: 4.15.1
Website Url: www.wildbikers.com