I borrowed a 5D from my friend. Man, it is really contrasty unlike my 40D. I did a minimum processing, and it is amazing. Hopefully, I get one cheap when the new one comes out. The picture below was taken with a 35mm f/2.0.
I'm glad you like both the camera and that lens. I had the 5D, but sold it before the price started to drop. I'm waiting patiently for the replacement.
This is an interesting composition and it shows you are trying to present both the girl and the environment. I do find my attention is divided and I get a sense of a "busy" picture. I'm not sure I like the look down shot.
Foreshortened figures are mostly not pleasant to look at. At least that is my reaction. I, too, think it is way too busy to have any realy center of interest.
I'll make a post about it soon. Look out for it. Maybe it's just me though (I came from first using a 40D so the LCD screen size might make a difference). My AWB on the 5D seems incredibly off as well. Greens appear yellow.
Try shooting in the "Landscape" setting on your 5D. I think this setting looks nicest straight out of the camera. As for white balance there is a setting buried in the menu somewhere that controls calibration. Make sure this isnt shifted around. (Sorry I sold my 5D waiting the 5D Mark II so I cant say exactly where).