Ray, since the E-mail had an image, I'm assuming it's HTML.
If you're familiar with HTML and know a little of what you're looking for, you can get look for the URL in the source code. It may take some hunting.
Using IE, open the E-mail, click on File, Properties, select the Details tab, then click Message Source. This will show you the HTML code. You can follow through the code until you find the spot where the image is being shown. The URL will show there.
Remember, it's really not proper to link to someone else's site without permission, so if you want to use it you really need to get an OK.
Another choice is you could just copy it. Right click on the image, and then save it. You could then put it on a site you control (web page, etc) and link to it there. Again, you really should have permission to use someone else's graphic.