Here is a cool trick you can add to make it look a little more stylized!

Not sure what program you're using to make this, but select all the colors of the body, so basically all the greens - then select a darker cool color (dark green or maybe evne dark blue in this case) and put a light gradient over it. It will add a little more depth to the picture!

It's hard to explain but this is what I mean:

@humanity I did what you said and it looks SO MUCH better! ^_^

@monkeyman04: Yah! Experiment with different colors like maybe use purple or something crazy, mix and match - generally you want to use cool colors for shadows and warm colors for highlights. You can also try doing this same technique on individual pieces like outline just the door and add a light gradient to it as well, the hood, the side mirror etc. Just don't go overboard! Glad it helped.

@humanity: I've done more gradient work and I feel like a dumb ass from not thinking of it. >_< Again thanks for telling me about it.

EDIT: (I don't really know what I'm talking about when it comes to design though)
Some inspiration:

Its flatter and only has 2 colours but I still think something similarly cool could be done.

https://www.behance.net/gallery/19267939/Porsche-911

https://www.behance.net/gallery/18995947/Ford-Mustang-GT350

Gallery

@cirdain: I like the design, but what I'm try to get is a pure outline (which I hope I did) and then a color that will somewhat match the original pic. At the moment I'm not an artist of cars (I wish I was). ^_^

Ok... This is the last one for the night. Thanks for the help @humanity

@monkeyman04: Lookin' good!