Recently I've been very suspicious of httrack behavior, as a result, I tested
it over this link - 

<http://www.edenpics.com/index.phtml?l=en&m=g&t=l&c=2&p=1>

I wanted to download all the images in the mountain category, as a result I
set the max internal depth to 4, why - 

1) the page <http://www.edenpics.com/index.phtml?l=en&m=g&t=l&c=2&p=1> itself.
2) The next page link
3) Link to image's page (which contains it's info but not the real image).
4) The image itself.

Unfortunately, with max depth as 4, it only downloads the images in the
provided page, if I set it to 5, then it works as expected, all images in the
mountain category are downloaded.

I'm not sure if this bug persists for max external depth, if you want I can
test.