There is more than one way to approach this issue and you began this thread by referencing php files.... and in the tpl_product_info_display.php file there is this code:
Code:
<!--bof Additional Product Images -->
<?php
/**
* display the products additional images
*/
require($template->get_template_dir('/tpl_modules_additional_images.php',DIR_WS_TEMPLATE, $current_page_base,'templates'). '/tpl_modules_additional_images.php'); ?>
<!--eof Additional Product Images -->
and it is placed after many things that display before it. Moving it up after the main image entry was what I was leading to. and there are a few clear both statements in this file that call for a new line. You will have to insure that the additional images have space to be presented. Do this through sizing of your site and images no matter if you do this by code file or through css.
As you seem close now you might continue with what you are doing or you might also look at the file??