Here's the deal. I have a website, on which there are a bunch of folders, each
containing a bunch of images. On the main page of this website, exactly one
image from each of these folders is shown. But the rest of the images are not
linked anywhere on the website, they are only stored on the server. But I can
see them by entering their url into a browser.

Now my question is, how do I download all of these images, and not just the
ones linked on the main page? Or is that even possible? I imagine it is, since
HTTrack can gain the folders from the main page, but I don't know how to set
it up to do what I want.