pr_demo_product_get_image.php

<?php
/**
 * If a product has an alternative featured image, display that on the archive page
 */
function pr_demo_product_get_image( $image, $product, $size, $attr, $placeholder ) {
  if( is_product() ) {
    // We're on a product page so just return the image
    return $image;
  }
  $product_id = $product->get_id();
  // Check if there's a custom image for the archive
  $image_url = get_post_meta( $product_id, 'pr_custom_archive_image', true );
  if( $image_url ) {
    $attachment_id = attachment_url_to_postid( $image_url );
    $image = wp_get_attachment_image( $attachment_id, 'woocommerce_thumbnail' );
  }
  return $image;
}
add_filter( 'woocommerce_product_get_image', 'pr_demo_product_get_image', 10, 5 );