Well, you could create a custom template file for that category. Get the category ID number, and then go into your main template directory. Open up category.php (if it's there), or archive.php (if it's not) and save it as
category-6.php, but replace "6" with the ID of the photo category.
Then, change the code of that file to not loop through posts, but instead just show one and break out of The Loop. Since I don't have access to your template to tell you exactly how to do this, the super-quick and super-dirty way that will almost certainly work is to just put a
break; right before the
It's probably designed to loop through a bunch of posts, and usually that loop is wrapped in
while( have_posts() ): the_post; and
endwhile; Right before the
endwhile;, you put a
break; which says, "Break out of this loop, and don't continue." Since it already finished the first run through, it'll just show one post, and then quit.
Then, the link to give is just http://your.site.com/category/photos/