You really should be using FOG 0.32 and sysprep’ing your images.

I would be using 1 image for all rooms, as long as they are from the same hardware set.
Simply enable / disable the ‘Hostname Changer’ service per Host.

In regards to the Hostname Changer not working:
[LIST=1]
[]Open or preferably ‘tail’: c:\fog.log
[]Look for: HostnameChanger
[/LIST]
Are there any errors reported? It may take a few minutes for errors to appear.

It uploads it via FTP, the file is not locally copied.

This is done for flexibility; The TFTP server does not need to be on the FOG server.

Great to hear you got it all working.