Well... you-ve got a nice picture there, that's for shoore.
But... something is... hmm... it's just a feel that something don't fit there.
Maybe it's a material on the main gun. I think it's to reflective. I sugest you to make something like ruff coroved, very low intense reflection over the bump.
I don't like that yellow type of atmosphere (but that's just my personal taste, so don't consider this) with this too yellow fog. Maybe if you try redish sunset?
And yes... acourding that this is sunset, covered with clouds and fog, and stuff, I think that your shadows should be much blured.
Also, is the position of the light on the right place? I ask that, becouse it seems to me that the shadows are maybe shorter then they should be.
Sorry for nitpiking, but you ask it.
I suggest you to add a bunch of little stuff that is easy to model, for the enviorontment (rocks, barrels, birds at the sky), also a nice DOF would be good.
Keep it up.