@mwarner Be warned, Mac OS X major system updates don’t just consist of the data on disk but more often than not there is also an upgrade to the UEFI firmware which you wouldn’t be able to simply transfer to the other machine. FOG can’t do this!
On the other hand you should be able to deploy an image to a completely empty disk. As Wayne said, we need to know which version of FOG you run to see if it could be an issue with an older version.
On you FOG server console please run
ls -al /images/<IMAGE-NAME> and post a picture or full text output here! By the way, there is no need to mask the image name. It’s just making it harder for us to help you.