I've been playing about with this scene since yesterday. I've had to finish off some modeling on the car and there's still some tinkering that needs to be done as well.
Mmm.... I'd probably try using reflectionmap or HDR dome to make those prizes stand out a bit more and give them that expensive look. Right now they're just reflecting the gray enviroment, which makes them look bit dull.
On first picture, car lighting doesn't match with the background. Building and car are casting shadows on opposite sides.
On second picture, car is too small and you're using some kind of studio lighting setup with multiple lightsources. Looking at the shadows cast around car, it gives the impression that there's 2-3 invisible lightbulbs hanging above the car.