- did you add the +.jpg +.png filters to download the images?- I saw an
"download near links" option in the documentation, maybe that could help
- when I used wget to download a site and I was connected through my mobile
phone, there was a problem that all the images were parsed (quality
degradation) by an external server (with the different ip/domain adress than
that of the site I was downloading). Maybe adding a filer with the IP adress
of that site would help (not sure if httrack handle IP's as links though).
- provide more info - the site adress, the filters you've enabled etc.

pozdro