Major light issues. I just think you should take this image, remove all areas that you have shadow in. And pick 1 point where the light is coming from, and just try your best to pretend seeing the lines of light beam down on the objects.. This way you can lay down the shadows to match.

Why does the sidewalk have tile? It looks like a bathroom floor. Fun concept, though.

Hmm . . . just noticed:

His right-most (our left-most) claw thing isn't as sharp as the others. Maybe add an extra pixel at the end?

...and the car glass looks like tin foil :P Still, well done :)

The door, the cars, and the man aren't to scale. Look at the door of the building and look at the car.

Other than that, the shadow of the side walk isn't in sync with the shadow of the man.

That guy's gonna get eateded.

Good composition.  I think the sidewalk on the right could use something though, like a fire hydrant or trash can, or maybe a cat with its hair standing on its back...

 

The shading needs some work.