Voices:
Add some minimal percussion maybe.. Stretch them out a bit more, and change up the instrumentation too, and you could have some awesome stuff here (it's pretty cool as it is, but adding doing some of that would likely make it more interesting.)
Try listening to more ambient to get a feel for how they write the stuff. Ambient songs are based on the idea of slow progression, and eventual buildup. They don't usually get too much louder overall, but things change, become a little more complex, or change instrumentation slowly, that sort of thing.
I really like Viel Of The Light, I'd only listened to voices when I wrote that first part. I like how it seems sorta complex, yet very simple at the same time.
