Sorry, I had a look and found that only members of the Group can download/upload photos. All you need to do is to go to
http://groups.yahoo.com/group/cypnature/?yguid=38299784 and request membership on top right. You should then be able to view the photo (may take up to 15 minutes for your membership to be inscribed, wait until you receive the Welcome message by e-mail).
There is no way to configure Yahoo Groups for non-members to view photos; I didn't know that. Sorry if I misled you.