Vibration in engine- help!

It could be anything really. There is obviously an oil use problem. The other plugs look rather goopy too. That kind of buildup could be bad rings, leaking intake gasket to the intake, guides, or valve seals, or a bad wire, or a bad plug...lol. If it was me, I'd put fresh plugs in, see if it clears up. If not, do a compression test on it and see if there's a sealing problem there. If it's low, pull the head.