Как то так
/admin/model/catalog/product.php
Найти
public function deleteProduct($product_id) {
Добавить ниже
$img=$this->db->query("SELECT image FROM " . DB_PREFIX . "product WHERE product_id = '" . (int)$product_id . "'");
unlink($_SERVER['DOCUMENT_ROOT'].'/image/'.$img->row['image']);
$img=$this->db->query("SELECT image FROM " . DB_PREFIX . "product_image WHERE product_id = '" . (int)$product_id . "'");
$i=0;
while($i <= $img->num_rows-1){
unlink($_SERVER['DOCUMENT_ROOT'].'/image/'.$img->rows[$i]['image']);
$i++;
}