Gabriel-
I don't think the mirrors have a right to get free hosting, and it's not hard to save them really if somebody wanted to.
Well, we don't make it exactly easy either, what with blocking all the spiders ..
If there's a concensus (and no copyright problem) to provide a big tar with all images for more convenience, then it's just a matter of adding it at download.wikimedia.org.
If it's OK for us to host the images in the first place, then it's also OK to put them into a tarball.
Regards,
Erik