Are you looking for a critique? If you are, then I would say the stance, and proportions are right on. I see the wheels are Photoshopped in. My main critique is that it needs more definition and detail and light source and reflection also needs a bit more detail. Not sure if you did the artwork was in Adobe Photoshop but it looks to be low resolution (a case of the jaggies on the outlines)...300 dpi is a good resolution. The roof line needs to be fixed a little.
I would say you are off to a good start! Keep working at it and you will find that you will become faster and better with each rendering that you do (it takes a lot of patience and determination).
It's all positive feedback which can only help you improve.