Listing Thumbnails Without Repeat

Howdy,

Semi-new guy here. I had a question about listing thumbnails. I’m running the latest version of WP (3.4.1) and am using a theme from Theme Trust (Uber). However, I am building a custom area to display articles on the home page. I have several boxes with the title and excerpt over an opaque background, and have it set up so that a background image can display behind all of it. I have managed to automate the retrieval of the excerpt and title, but am having trouble forcing ordered retrieval of the thumbnail and placing it as a background image in the box of its respective post.

At first, it used the last thumbnail as the background image in each box, but with the code below (which I thought would fix my problem) it instead displays the second to last thumbnail in each box. And the more times I put $image_url[0] inside of my array, the further back in the thumbnails it goes (you can see the current state of this situation on the test site I’m running). The code is applied inside the loop on my home page template file, and is as follows:

<?php while (have_posts()) : the_post(); ?>
		<div <?php post_class('small'); ?>>
		<?php
   			$image_id = get_post_thumbnail_id();
   			$image_url = wp_get_attachment_image_src($image_id,'cia_post_thumb_ra_big');
			array_push($array_image_url,$image_url[0]);
		?>
		<?php require 'ra.php'; ?>
		</div>
	<?php endwhile; ?>

Then inside of my CSS (ra.php), as my background-image:, I am placing url(<?php echo $array_image_url[0]; ?>). And then for each successive box ID (eight in all) I am replacing the 0 with 1, 2, and so on. This was what I thought would solve my problem. Am I misunderstanding arrays or array_push? Is there a better way to solve my problem? Is my syntax off? I have tried several things, but none of them have worked so far.

Any help on this issue would be much appreciated, as my experience with PHP and CSS is very limited.

Thanks!
Ben