If you want to add a rain reflection and you have some time on your hand just go into CMX viewer load the same car with the same skin and the same wheel colour. Try to get the most exact same perspective as in your screenshot.
As soon as you have it try to only move your mouse down (clicking the right mouse button). If you are viewing the car from underneath unable the sky texture, make a screenie and paste it into your edit. If you cut the car out and then mirror it you can go on with editing a reflection.
Edit: And for the rain... while in the foreground drops look realistic, it adds a lot to the immersion if you tone the background with a slight amount of rainy grey... because in the distance the drops look more like fog.