Adding Theme Background Image

I currently have 4 images on rotation for background. Here is the code.

<?php get_header(); ?>
<!--START BACKGROUND IMAGE-->
<div id="pause">
	<a href="warp()"><img src="<?php bloginfo('template_url'); ?>/images/overview.jpg" name="targetimage" border=0></a>
</div>
<div id="body-container">
	<div class="fadein">
		<div class="planning"><a>Start-Up Consulting Services</a>
	</div>
	<div class="infrastructure"><a>Strategic Planning</a>
	</div>
	<div class="time"><a>Business Consulting Services</a>
	</div>
	<div class="budget"><a>Change Management Consulting</a>
	</div>
<div class="interim"><a>Interim Services</a>
	</div>

</div>
<!--END BACKGROUND IMAGE-->

For Interim Services I am trying to add a different image. But cannot find the location of (myimages[4], this.href)

Where are the image locations stored to add it?