Very interesting question. Let me make sure if I have understood the requirement fully.
You wanted to show a list of URL's and when the user makes the selection you wanted to see the screenshot of the URL's homepage. And you dont want to manually capture those screenshots but you wanted to dynamically get the screenshots, is this right?
I am sure you must be aware of using Bundle & Info Load to integrate external objects like images in QlikView. However, you wanted these images dynamically because your URL changes frequently... is this right?
I'll look forward to hear from you.
Cheers - DV