Good question, Frank.
The screenshots below show you the steps for adding photos that are stored on the TLR server and appear as tiny thumbnails at he bottom of the message. Like it works at RetouchPro.
There's an option right under the text box for adding attachments. You click on that and it will open up the items or attaching a photo.
Conrad's technique displays the image inline, like it works at DPReview. And, like with DPreview, this option is an external link. The photo is stored whereever on the Web. If the resource moves or is deleted, the link will no longer work. There is no copy stored on the TLR server.
(So, Conrad, don't go moving that nice frame!