If you have a URL that shows "just" the photo---test this by pasting the URL into a browser ......just add the "image" tags. I would guess that your URL is AFU meaning it is "framed" or something part of EG a flickr page etc
Example if I want this photo from this page.......
and all I do is add the "img" tags to front and rear, it looks like this, which I cannot type as the software will not show it LOL
URL, then add tags.........