WPB WooCommerce Product Slider (Free version) image size change

functions.php

<?php

/**
 * Add this code on your theme functions.php file
 */

add_filter( 'wpb_wps_product_archive_thumbnail_size', 'wpb_wps_product_archive_thumbnail_size_update' );
function wpb_wps_product_archive_thumbnail_size_update( $size ){

	$size = 'large'; // your image size

	return $size;
}