The treatment does look unnatural, but the firies were happy and that is of course (as far as I see it) the main thing. It was for a promotion - something you want to be eye-catching and get people looking at it - and I don't think I naturalistic-realistic treatment would necessarily have achieved its aims at all. Nick made conscious decisions about the look and feel of the picture and the client was happy with those decisions - job well done!
Having said that - yes, the repeated cloud is odd (I can't see three repeating patterns, though). The perspectives do look strange - but is that just because there are two little guys and two massive guys (ie, they are actually very different sizes in real life)? You have to work with what you're given, but it would have been better if the big guy in front had a white arrow instead of the black one - it would have exposed better and stood out more and also matched the colour scheme in the logo (as on their t-shirts).