Im really stuck.

I want to offer customers extra files from a web site. (Assume 100 items)
This would involve showing a picture for each and allowing a download of the selected item to the documents folder.

I could get a list of the files by downloading a json file and decoding it.
But getting the thumbnail pictures may not happen fast enough to allow me to display them.
if everything is local, then I can use a derivative of the slide view example code to display the choices.
But it expects all the pictures to exist before it starts, and I can't assume all the images will be present.

Truth is, a web popup would be better.. I think I should be able to use the post method to see if someone has selected an item off the displayed page.
But I found that it is so heavily cached that if new items are added to the web page, the webpopup simply ignores it. Its like its cached forever.

So:
Imagine a shopping cart, with a set of choices in a web page.
How would anyone else show that to a user, and then download some file in response?