The rear wheel is massively off, you can see far too much of it and it is too wide - line it up with the base!
The wheels, diffuser and lights are also terribly grainy and low in quality
I'd leave out the rain too if i were you, it makes the whole thing look a lot more fake, with random rain falling all in different directions, and massive water drops and splashes that just look completely unrealistic
Ideas and brushing is good though, so concentrate on making them look as good as possible, and I think soon you will be pro
