What different frame materials have been used?
Bones

Density average 1.84 g/cm³ for dry bone.

This would be a pretty bad material for a bike frame, and its quite likely that any bone bike really has a metal core in the middle.



Advantage 


Shock factor, or as part of a costume ("Death rides a Pale Horse")


Disadvantage 


Bones aren't particularly structural by themselves.  A skeleton is made from tendons and cartilage and soft tissues as well.
Durability - bones that dry out get brittle and will snap easily.
Intolerant - A crack could go from a minor hairline to a full break very quickly.