Good job on the proportions, texturing and shading! I'm not familiar with this particular incarnation of Ghost Rider, but that costume looks sweet! Great contrast of the orange and green too. I really dig how the light from his fire chain reflects of the right-side armor plates.
The only thing that really sticks out to me is the flaming skull: the shape of the flames make it look like they were drawn with a simple circular brush in MS paint. I'd recommend trying to taper each flame into a point so that it will look a bit more natural.