If you think about it the concept behind a dropdown select it's pretty simple. For what you're trying to accomplish, a simple <ul>
will do.
<ul id="menu">
<li>
<a href="#"><img src="" alt=""/></a> <!-- Selected -->
<ul>
<li><a href="#"><img src="" alt=""/></a></li>
<li><a href="#"><img src="" alt=""/></a></li>
<li><a href="#"><img src="" alt=""/></a></li>
<li><a href="#"><img src="" alt=""/></a></li>
</ul>
</li>
</ul>
You style it with css and then some simple jQuery will do. I haven't tried this tho:
$('#menu ul li').click(function(){
var $a = $(this).find('a');
$(this).parents('#menu').children('li a').replaceWith($a).
});