I downloaded the PS3 Themebuilder from lili-chan. It has an option to add sound files. The sound files you need have to be VAG. files. You can download loads of sound files from a variety of places, just type 'sound files' into google. However, it is difficult to download VAG files. Once you have downloaded sound files of any type, you then need to download a converter to convert them to VAG. I use Awave.
How did you manage to change the sound files?
Great job! The other folklore theme I found was horrible, this one looks awsome! 10/10 :D