A photo site doesn't appear to be the obvious site store store arbitary binary data but it actually turned out to be quite easy (the parlous state of Flickr modules on CPAN and the slightly crackfuelled Flickr API notwithstanding).
First we split our data into chunks and secrete them in the Least Significant Bits of each pixel of the image. Then we upload these to Flickr and group them altogether in a set which we name after the filename. Et voila. Arbitary data.
The default image is, appropriately