A while ago I run into a program which allowed to see a list of all the resources used by a site (images, icons, videos, files, scripts, anything).
You could see the folder structure and upon clicking the /images directory for example you were able to see all the images for the page.
I also recall to stumble upon something similar on a browser that had the capability to "show resources" or something of the sort.
So it could be a program or a browser (+extension?).
I have the worst memory. I can't recall what it was so I wonder if anyone here actually knows.