Thanks for the comment...
I looked more thoroughly, and results that files are stored in the database... in some weird manner. There's no blob field in the fs_version table and there IS a "POSTGRESS don't know what to do" comment in the SQL documentation, but is a fact that the thing works. Somehow. Anyone could enlighten me on what's the deal with postgres and blobs?
So, static-files wouldn't work, but at least i found where the blob is served, so it's all about checking the mime type and using ad_serve_html_page or whatever it is called.
Thanks,
Jorge