Update for the newest version of flickr iframe:
HTML Code:
<iframe align="center" src="https://www.flickr.com/photos/{param}/in/photostream/player/" width="800" height="547" frameborder="0" allowfullscreen webkitallowfullscreen mozallowfullscreen oallowfullscreen msallowfullscreen></iframe>
The user must now copy both their user name and the photo ID. That's not a problem, they're side by side in the url, so it's a simple cut and paste.
Tested and running on my forum, presented as is, no guarantee.