I currently use a Windows 7 VM with Serva64 in order to boot machines off the network and run tests/windows installations without needing to use physical media (we are a PC repair shop), is there a docker container which can give me the same functionality as that of Serva64?

There is a TFTP server available in Apps, but no further development on it is taking place.  I'm sure you could find tons on a full dockerHub search.