I think I've seen somewhere skeleton figures on war chariots and the wheels of the chariots were made from bones.
...which is weird (and what did the wheels look like when they were alive?)
You need material for a chariot, you've got bones, sod it - sentient bone chariot.
That's the whole idea behind the age of sigmar bonereapers - they take a bone tax from their territories and then use necromancy to fuse the bones into new constructs.