OK, I get now that it's not displaying multiple images for a product that's proving difficulkt, but getting the multiple images into a pop up window. I've not done this, but here's how I would go about it. But please note, it's an untested approach not a solution.
Edit the foillowing line in my english.php file
PHP Code:
define('TEXT_CLICK_TO_ENLARGE', 'larger image');
Create two new directories in my template called popup_image and popup_image_additional and move the respective tpl_main_page.php from template_default into each.
Make a copy of tpl_product_info_display.php in your template directory and comment out the code between <!--bof Additional Product Images --> and <!--eof Additional Product Images --> to stop the additional images from also appearing on the product page.
Add a copy of the code commented out in the previous step into the tpl_main_page.php in the popup_image directory.
By this point you will hopefully have a popup window that displays the original images and the additional ones. However, there's also a good chance that you won't and some tweaking may be necessary. Hopefully other forum members will spot and post about any misconceptions that I may have.
If you then want to display one of the images at a time like the site you are referencing, you will need to start breaking the php apart to be able to identify and load one image at a time, and create the links to move between them. If you further want to make it look really snazzy, then control the whole thing with one of the many image swapping javascript scripts available (a quick search of hotscripts.com will yield plenty).
No guarantees but hopefully enough direction to help you move forward or at least understand the complexities involved and why nobodies given you a quick solution.