maybe add a thin coat of matt varnish over the top of the paint to avoid scratches and scuffs?

I love the idea of upgrading standard 'phone cables - have you tried using different types of solder, or even so called 'audio grade solder' to lift the performance further still? Great photos by the way, would like to see the final heatshrunk cable :-)

The free white earbuds that come as standard with any Apple iDevice - crap sound, and won't stay in the ear!