Sorry for being so straightforward, but in my opinion, the only good things about these girls are their models and textures (NOT materials). It would be better if you had a better skin material and somewhat nice posing, even with lower-res models, because the current posing ruins it all. Also I think that their outfits should match the cars' liveries.
The poses are unnatural, stiff and lifeless. They're both staring into nowhere. Look at the facial expression on the girl on the left, is she a zombie?
Yeah, and mirror those sidewall textures already
Aaand the S15 lights are nice
What renderer are you using anyway?
Also why are there no shadows in the "chavs showing off" renders?