Recently active topics in Pownce tagged with photo

I saw this photo appearing in Pownce: http://pownce.com/holgr/notes/765960/ - so I know that it's possible to get a picture to display.

But when I upload a picture file, it shows up as a link, with no thumbnail. Similarly, when I embed the URL for a pic in the message text, it shows up as an embedded link, with no picture.

What are other people doing that I am not aware of?