Hi there... just so happens that I'm redesigning a site where I wanted to do something similar, to make it easier for visitors to navigate the category pages... I don't know if this will help you, but here's what I've done:
In the "archive.php" file, I altered the code from this:
Code:
<h1><a href="<?php the_permalink() ?>" rel="bookmark"><?php the_title(); ?></h1></a>
to this:
Code:
<h1><a href="<?php the_permalink() ?>" rel="bookmark"><?php the_title(); ?></h1>
<p><img src="http://webwenchginger.com/wp-content/uploads/2009/12/full-story.png" /></a></p>
I choose to use an image, but you can use a text link... either way works. You can
see it live on this page. (I'm not done with this site yet, but you'll get the idea.) Hope it's ok that I posted this here... hope it helps! :)