Ok I worked it out, you can't link an image with an external link, so using:
<img src="http://websvr/osticket/images/Picture.png" alt="Picture">
Wont work, but:
<img src="/osticket/images/Picture.png" alt="Picture">
Will work, if you use the full address osTicket sets it as a span with a non local source (it still shows in the HTML but doesn't render).