Actually, it may be relevant..."leaf masks" and "foliate heads" turn up in Mesopotamia and Lebanon by the first and second century AD. So I would argue that if they are pagan, foliate heads are more likely to be either middle-eastern pagan, or classical pagan, and brought west as part of Christianity--just like angels, etc.

I agree with you, though, Pip, that that isn't what most new age green man fans want to believe...they mostly want to believe in a Celtic pagan provenance, which is very tricky to prove.