https://dl.fedoraproject.org/pub/alt/stage/20-Beta-TC4/Images/x86_64/
I tried out the x86_64 image and it seems to be basically sound, with one big caveat. Cloud-init is still waiting to be updated -- see https://admin.fedoraproject.org/updates/FEDORA-2013-17760/cloud-init-0.7.2-7... and test and give karma, please. (This is why, for example, the root partition isn't growing.)