I only recognized Franchitti's helmet, but I didn't knew that it is his IndyCar...
The GP2 cars look really good, seems they are very well made (-> with this I mean you can't see single pixels were for example white goes over into blue because you softened everything). I like that very much, it's exactly how I work, too.
I would have probably included the big winglet in the bitmap, but if you make it or leave it depends on the style of the painter, so I think it's ok like this as well.
Maybe you could install a new carshape that looks more than the GP2-series-carshape!? That goes for the IndyCar as well, then we would have maybe recognized it as IndyCar

I dunno if you ever used other carshapes than the original one, if not I would suggest you to give it a try, it's not to difficult!
BTW: Is that GP2-series carset your first work!? By the quality it has I would say no...
