Change the WooCommerce product category image size

function.php

<?php
// Do NOT include the opening php tag.

/**
 * Change the WooCommerce product category image size
 *
 * @author Nic Beltramelli
 */
add_filter(
	'subcategory_archive_thumbnail_size', function ( $small_thumbnail_size ) {

		$small_thumbnail_size = ('woocommerce_gallery_thumbnail');

		return $small_thumbnail_size;

	}, 10, 1
);