I would try a couple of things:
1. Try substituting an English image in your Italian document. That will tell you if
the issue is with the image files.
2. Try using fop with the -foout option to generate a .fo file for each of the
English and Italian. Then peek inside the FO output to see if the
<fo:external-graphic> elements have different properties.
Those two steps should narrow down the possibilities.
Bob Stayton
Sagehill Enterprises
bobs@sagehill.net