If you were to view one of the images in my WordPress gallery, such as my Minnesota State Fair – 2009 gallery, and view one of the images.  You will see a previous and next image on the bottom of the image page.  As you may of already of guessed, the next and previous images are all part of the way my theme handles image pages.

In order to do this, I needed to add the below snippet to my image.php file.  You should already have a “navigation” section, find it, and replace it with the below code (MAKE SURE YOU BACK UP YOUR IMAGE.PHP FILE FIRST).

<div class="image-navigation">
	<?php $attachments = array_values(get_children( array('post_parent' => $post->post_parent, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => 'ASC', 'orderby' => 'menu_order ID') ));
	foreach ( $attachments as $k => $attachment )
		if ( $attachment->ID == $post->ID )
			break;
	$attachments = array_values(get_children( array('post_parent' => $post->post_parent, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => 'ASC', 'orderby' => 'menu_order ID') ));
       $next_url =  isset($attachments[$k+1]) ? get_permalink($attachments[$k+1]->ID) : get_permalink($attachments[0]->ID);
       $previous_url =  isset($attachments[$k-1]) ? get_permalink($attachments[$k-1]->ID) : get_permalink($attachments[0]->ID);
	if ( wp_get_attachment_image( $post->ID+1 ) != null ) { ?>
		<p class="attachment">
			Next Image<br />
			<a href="<?php echo $next_url; ?>"><?php echo wp_get_attachment_image( $post->ID+1, 'thumbnail' ); ?></a>
		</p>
    <?php }

    if ( wp_get_attachment_image( $post->ID-1 ) != null ) { ?>
        <p class="attachment">
            Previous Image<br />
            <a href="<?php echo $previous_url; ?>"><?php echo wp_get_attachment_image( $post->ID-1, 'thumbnail' ); ?></a>
        </p>
    <?php } ?>
</div>