Mirroring of the images are disallowed in the robots.txt rules. 

<http://www.pintura.aut.org/robots.txt> has the followin content:

-----
User-agent: Mediapartners-Google*
Disallow:
# No queremos robots
User-agent: *
Disallow: /BU04/
Disallow: /SearchAutor/
Disallow: /SearchProducto/
Disallow: /4DPict/
Disallow: /ImgBanners/
-----

The image files you want is probably in the directory /4DPict/ ?
You have to tell HTTrack to disable robot.txt rules. It is done from the
command line with the parameter -s0 or from the GUI in the 'Spider' pane.   

Read more about robot.txt rules here:
<http://www.httrack.com/html/faq.html#Q1b1> and here
<http://en.wikipedia.org/wiki/Robots.txt>