You want to display all images but you don't want to load all of them (or load the information of them). In fact, this is not possible, because javascript is working in user browser and it can only display images which are loaded on the site.
If you want to display all the images from category, you need to use iframe method as it loads allways current image (in fact this can be compared to ajax - everytime you click on next image, it will be loaded from server)
But the javascript methods are working other way (don't ask me why because I am not creator of the javascript nor creator of the javascript methods used for displaying popup methods)
The javascript method can only work with images which are loaded on the site (you don't need to display the images but you need to load all the information of the images). This is the internet/javascript/html/browser feature.
https://www.phoca.cz/documents/50-phoca/ ... al-advices
Jan