EDIT:
I am going to revise this from 2 stars to 5 because from what I can see the issue I am having is with Archive.org and not the add-on itself. I have determined the images that weren't downloading were ones that were not true direct links to images, rather they were in some sort of frame added by Archive.org that was preventing the add-on from finding the images. This frame seems to be used at random by Archive.org. On some websites they use it, on others, they don't. A true direct link to an image on Archive.org can be revealed by the URL; it will show "im_" after the date/timestamp in the address. Whenever it shows "Im_" the images download fine and there is no HTML source to look at, it is a direct link.

When there is no "im_" in the archived image URL, it looks like a direct link to an image but it is not. The page source can be viewed as it is considered a webpage not an image.

So yeah, this is not the add-on's fault but a flaw with Archive.org. As far as I can tell this add-on works 100% to download images conveniently.

ORIGINAL REVIEW:
At first it was working good but have not had much success lately. For some reason, it doesn't work on certain archived websites on Archive.org. It singles out entire archived domains, I don't know why. There doesn't seem to be a discernible difference between two different archived websites but on one website image-only tabs will download fine, 100%, but on another, 0 images will download, 0%. This is not a case of maybe the images didn't archive. No, the images are opened up successfully in the tabs. It appears to be singling out particular domains, probably not intentionally, but some sort of glitch I guess. Simply put, it works on some archived domains and not on others, and it seems to only be affecting the direct links to images (image-only tabs), so for example, the thumbnails on those affected domains still work. Odd! Very odd!