good for your first, but i dun like the white area.
Also u could add a bit flow
Work on lighting,blending
Remove the splatter brush or wut it is in the right.
It looks like the car is flying, try to add a ground or smth to the sig. ( My opinion)
great... very good... though i agree with ali... it needs to either have more POP to it... or a little hue .-.