I was also planning to test but I was confused, what did you edit at "Name" in example.bat file? I guess we have to enter the name of the certificate and I didn't find any certificate in all the file I have downloaded.
BTW, can you show me the example script you have used, I am talking about the edited one.
Edit: Did you check the "read and write" box in gimagex before mounting your image, secondly I can see double slash after "windows" in the path of the files. These are the two issues you need to focus.
And regarding locale name, its for language I guess, if you are trying to change the English text you better leave it default i.e. en-us, if not then edit it acc to the language. I am not sure but this should be like this, that is what I think.
Though I have manged to change the boot animation in the boot.wim and my installation also started without giving any problem and that too with custom animation but it didn't reboot after "Installing Updates" and gave me some error.