1. NEED LIGHTS
2. NEED MORE LIGHTS
3. And when you've got lights, ADD MORE LIGHTS!

I'm sure you're seeing the same image we are. Tell me, can you see any detail in the dark parts? The smooth shaded/wire frame looks fine, but all of the other things are too dark.

REASON:
The contrast between the dark greens of your image and the bright gray of the forums is hiding all of your details.

SOLUTION:

1. Get rid of the green background. I'm sure it's an artistic thing, but get rid of it. Use a neutral color like, ohhh I don't know... GRAY.

2. Add even just one light to your scene.
"In the absence of light, darkness prevails" - Dr. Trevor 'Broom' Bruttenholm, Hellboy