Posting a pic is a pain in the rump, however as I am the only one who seemed to figure it out here is how you do it.
The photo will have to be hosted by a third party on the web this can be you at your google photos or something, or another web site that allows the linking. I think you can also up load photos to your profile here then link but never tried it.
Next copy link, use photo icon above menu, past link, I like to add an constraint on mine. You will also notice not all links and file types work, this is a trial and error thing, but I know Pinterest is generally a no go. But Deviant Art works.
Hope this helps.