I'm too newbie to comment zeantsoi post ;(. So here his what I needed to do to solved on OSX on 10.9.1 the
IOError: decoder jpeg not available
1) install Xcode tools (open your terminal and execute: xcode-select --install
) - taken from this post: Can't install PIL after Mac OS X 10.9
2) install libpng and libjpeg package (combo installer) from this link: http://ethan.tira-thompson.com/Mac_OS_X_Ports.html
3) reboot (not sure it was mandatory)
4) Re-install PIL with run pip install -I PIL
(as I had initially installed PIL before having the issue)
Hope this help and don't confuse more ...
_oho