Showing related post thumbnails using Efficient Related Posts for WordPress

show-related-thumbs.php

<?php
function range_related_link_content( $content, $p, $settings ) {
	// These two lines allow you to specify a default image if one doesn't exist.
	if ( empty( $p['post_image'] ) )
		$p['post_image'] = '<img src="' . get_template_directory_uri() . '/images/icons/default-related-thumb.png" />';

	// Prepend the post image to the content and return the content
	$content = $p['post_image'] . $content;
	return $content;
}
add_filter( 'erp-related-link-content', 'range_related_link_content', null, 3 );