Meh, let me comment on this, I disagree with most of the red parts.
Looks empty: add some doodads to the sensors/antennae.
Continue the slope: That'd just make it a Star Destroyer, and he's already doing that, just not the way you are illustrating in that image.
Maybe green it: Nah, don't, maybe a good idea to add a doodad/glow in between that curvy section and the arm/strut going back to the ship.
?:I agree with this one, maybe turn them inwards to the ship a bit, or don't make them stick out that far, they break the flow. Or then again, maybe not, since it follows the flow of the triangular section protecting the arm/strut.
Shading: totally not needed, seems to me like you allready did that, and the engine seems to be on the same height anyways.
Only thing you really have to do now is adding doodads/glows and weaponry, it seems finished to me.
EDIT: Engine flare should be coming from an engine, not constantly being there being all like, LOOK AT ME I'M GLOWING I'M GLOWING.
And preacher, now you've got me, a glow by shading, how the hell do you make something glow by shading it, I think you mean using fake aegis to make a section glow?