@gafferwiles When you use a NAS as a storage node there are a few things that happens.
FOS Linux (the OS that runs on the target computer) loads the image from the target computer onto the storage node (FOG or NAS) using NFS. The files are uploaded using NFS to /images/dev directory which is read write access. Now the user ID and password comes into play. The management user ID and password is used because the FOS Linux OS connects to the storage node using FTP to move the raw data files from /images/dev/<mac_address> to /images<image_name> directory. So you need to make sure the management user ID and password has rights on the NAS to login via FTP and can execute the mv command to move the files.