I want to insert a contact image into a message template. This will be used to print PDF "info sheets" about contacts to include their photo.

Simply inserting the token {contact.image_URL} of course only displays the image URL in the PDF. 

If I use something like  <img src="{contact.image_URL}" width="100" height="100"> I get a missing image icon. I have tested with contacts that do have contact images.

How can I go about this?