I have a GreaseMonkey script on Firefox that makes a BBCode linked picture for Flickr. I don't know why Flickr doesnt have that option already.
But if you don't want to get into GreaseMonkey, you can:
Make several blank lines in your Cellar reply box. Put the cursor in the middle of them.
right click on the picture on the Flickr page, and copy the picture location.
Click

and paste the image location. Delete ",v=0" from the end.
Copy the url of the picture's Flickr page.
Highlight the picture in the Cellar's reply box, and click

, and paste the URL.
It's several steps, but it works. Plus, you might get a bit of traffic to your Flickr stream.