nielso

Oh wow! I feel dumb now! Thanks for taking the time alchymyth 🙂
For those that wish to use this snippet in the future here is the code in its generic entirety:

<!-- Use this navigation code (only) in your single.php template -->

<div id="post-nav">

<?php
// Newer posts
$postnav_next_post = get_adjacent_post(false, '', false) ;
$postnav_next_post_id = $postnav_next_post->ID;
$postnav_next_post_thumbnail = get_the_post_thumbnail($postnav_next_post_id);
?>

<?php if ($postnav_next_post != null) : ?>

<div class="post-nav-next">

   <?php if ($postnav_next_post_thumbnail != ''): ?>
      <?php echo $postnav_next_post_thumbnail; ?>
   <?php else : ?>
       <img src="<?php bloginfo('template_directory'); ?>/images/default-90x90.gif" />
   <?php endif; ?>

   <?php next_post_link('%link', 'Forward', FALSE, 3 ); ?>

</div>

<?php endif; ?>

<?php
// Older posts
$postnav_prev_post = get_adjacent_post(false, '', true) ;
$postnav_prev_post_id = $postnav_prev_post->ID;
$postnav_prev_post_thumbnail = get_the_post_thumbnail($postnav_prev_post_id);
?>

<?php if ($postnav_prev_post != null) : ?>

<div class="post-nav-previous">

   <?php if ($postnav_prev_post_thumbnail != ''): ?>
     <?php echo $postnav_prev_post_thumbnail; ?>
   <?php else : ?>
     <img src="<?php bloginfo('template_directory'); ?>/images/default-90x90.gif" />
   <?php endif; ?>

   <?php previous_post_link('%link', 'Back', FALSE, 3 ); ?>

</div>

<?php endif; ?>

</div>