I never intended to offend you, sorry if I did. What would help is to try posing your own body and take pictures. Pay special attention to the pelvis, spine and weight distribution. Try reading a book on posing.
This isn't even a WIP, this is a fume/madcar test, why would I bother setting up lighting? To spoil my render times to even a greater value than they are now? No, thanks, I'm not a mazochist.
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?
Edit:
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?
Ditched the fresnel reflections for the "windshield and other glass" material, rotated the HDRI so it fits the background, and some minor fixes here and there.
Also, I'm messing with FumeFX and made a new numberplate
First, ensure there is no plane obstructing the view (Brazil has this somewhere in the render settings), then check if the image is in your environment slot and viewport background. Then it should work.