custom field from tag pages

Hi guys

I use custom field to post an image thumbnail for posts with certain tags. I use the custom field name ” AppLogo “

I was wondering if there is any way I can show say random posts in the sidebar. But instead of the text links I want the Custom Field Thumbnails to be shown which links to the post url.

For categories I can get this using this

<?php
      $random_query = new WP_Query(array(
      'post__not_in' => $do_not_duplicate,
      'showposts' => 4,
      'cat' => 2704
      ));
      while ($random_query->have_posts()) : $random_query->the_post(); ?>
<div style="text-align:center"><a>" rel="bookmark" title="<?php the_title(); ?>"><img src="<?php $values = get_post_custom_values("AppLogo"); echo $values[0]; ?>" alt="wp7-games" width="150" height="150" border="0" /></a></div>
    <?php endwhile; ?>

but could not figure out how to get the same thing done for tags , for categories i just need to chage the ‘cat’ => 2704 to the desired category id