For easy usage, here is query for related custom posts through custom taxonomy. Do changes for customposttype and customtaxonomy and of course use your CSS classes.

<?php

// get the custom post type’s taxonomy terms

$custom_taxterms = wp_get_object_terms( $post->ID, ‘customtaxonomy’, array(‘fields’ => ‘ids’) );
$cat_samelevel = $custom_taxterms[0]; // choose post with same level or parent level

// arguments
$args = array(
‘post_type’ => ‘customposttype’,
‘post_status’ => ‘publish’,
‘posts_per_page’ => 0, // you may edit this number
‘orderby’ => ‘rand’,
‘tax_query’ => array(
array(
‘taxonomy’ => ‘customtaxonomy’,
‘field’ => ‘id’,
‘terms’ => $cat_samelevel
)
),
‘post__not_in’ => array ($post->ID),
);
$related_items = new WP_Query( $args );
// loop over query
if ($related_items->have_posts()) :
while ( $related_items->have_posts() ) : $related_items->the_post();
?>

<div class=”three columns”>
<a class=”link” href=”<?php the_permalink(); ?>”>
<?php $thumb_id = get_post_thumbnail_id();
$thumb_url = wp_get_attachment_image_src($thumb_id,’category-img’, true); ?>
<div class=”category-img”>
<img class=”inline” src=”<?php echo $thumb_url[0]; ?>” />
</div>
<div class=”text inline”>
<p><?php the_title(); ?></p>
</div>
</a>
</div>

<?php
endwhile;

endif;
// Reset Post Data
wp_reset_postdata();
?>