Replacing the featured image with any other internal image of a post (only for category page)

category_post_image.php

<?php //* Remove this line

add_filter( 'genesis_get_image', 'gd_category_post_image', 10, 6 );
/**
 * Replacing the featured image with any other internal image of post 
 * if there have more than one image and not set as featured image
 * 
 * @author  Chinmoy Paul
 * @copyright Copyright (c) 2017, Genesis Developer
 * @license GPL 3.0+
 */
function gd_category_post_image( $output, $args, $id, $html, $url, $src ) {
	$feat_image_id = NULL;

	//* Execute the code if you are on category page
	if( is_category() ) {

		//* get featured image ID if you have
		if ( has_post_thumbnail() )
			$feat_image_id = get_post_thumbnail_id( get_the_ID() );

		//* Getting all attachments of a post
		$attachments = get_posts( array(
			'post_type'   => 'attachment',
			'numberposts' => -1,
			'post_status' => null,
			'post_parent' => get_the_ID()
		) );

		if( $attachments && count( $attachments ) > 1 ) {
			foreach ( $attachments as $key => $attachment ) {
				//* Excluding the featured image
				if( ! empty( $feat_image_id ) && $feat_image_id == $attachment->ID )
					continue;

				//* Getting first or another image ID
				$id = $attachment->ID;
				break;
			}

			$html = wp_get_attachment_image( $id, $args['size'], false, $args['attr'] );
			list( $url ) = wp_get_attachment_image_src( $id, $args['size'], false, $args['attr'] );

			// Source path, relative to the root.
			$src = str_replace( home_url(), '', $url );

			// Determine output.
			if ( 'html' === mb_strtolower( $args['format'] ) )
				$output = $html;
			elseif ( 'url' === mb_strtolower( $args['format'] ) )
				$output = $url;
			else
				$output = $src;
		}
	}

	return $output;
}