There's a lot of beautiful and clever pictures in this contest as brecklundin noticed ! Really stimulating
But, working with colors and meanings could be misleading in some countries I guess, even in our global world
There are some good books about it ... especially for web design.
IMHO one more tricky thing about these contests in general is the size of the pictures. For example, this one may fit the green "environment" idea (even if the blured main subject is white), but most of it is out of focus, and resized for the contest I guess it would be completely messed up, doesn't it ?
Even like this... did you saw the bird ?
Anyway, it sounded too much like an advertizing for a well known car
... and the next generation has already reached the market !