Random Posts from same category

Hey gang,
I’m working on a script that will pull recent posts in the same category. I’ve got it working, but it’s pulling the most recent 6 posts when I’d really like to be pulling 6 random posts from the category… I’ve spent hours trying to resolve this but alas my PHP skills aren’t awesome… any help would be GREATLY appreciated.

Here’s what I’ve got:

<?php
	// get other posts from this category only as related posts //
	$backup = $post;  // backup the current object
    $categories = get_the_category($post->ID);
    if ($categories) {
        $category_ids = array();
        foreach($categories as $individual_category) $category_ids[] = $individual_category->term_id;

        $args = array (
            'category__in' => $category_ids,
            'post__not_in' => array($post->ID),
            'showposts'=>6, // Number of related posts that will be shown.
            'caller_get_posts'=>1
        );

        $my_query = new wp_query($args);
        if( $my_query->have_posts() ) {
            while ($my_query->have_posts()) : $my_query->the_post();
      ?>
                <div>
                <?php $image = get_post_meta($post->ID, 'article_image', true); ?>
                <a href="<?php the_permalink($post->ID); ?>"><img src="<?php echo $image; ?>" alt="<?php the_title(); ?>" style="height: 90px; width: 90px; float: left; margin: 8px 8px 0px 0px; border: 1px black solid; padding: 0px;"></a>
                </div>
			<?php
		endwhile;
	  }
	  $post = $backup;  // copy it back
	  wp_reset_query(); // to use the original query again
	}
	?>