As far as networking, I don't think using fotoup.pl would be a good idea. It requires LWP::UserAgent, which doesn't come with the standard OS X install, so it could confuse the common user or complicate the program's install process if it has to install it for them. Also, Cocoa's NSURL functions won't work because it doesn't seem to support the PUT method... or I haven't seen any samples of how to. So, back to good old sockets.
Also, I noticed new accounts were locked on PicPix. Could I get one for testing purposes? I thought I already had one, but if so I forgot my login and/or password. I'm going to have to take down my test server because I need some of the hardware and I need to sell some of the rest.