"zero replies detected, entering critique mode"
Allrighty. What's this missile for? Is it just a standalone picture or for a game or something? Just for practice?
Well then, it's a great piece for that purpose. There's a cylinder that meets with a sphere, so if you can handle those primitives, now you can blend them together.
It's very flat at the moment and what you should do is move the light away from the same plane with the missile. It'll make the shapes pop out better if you pull the lightsource towards the viewer.
Currently the tip of the missile suggests a different perspective from the rest. You could make the area around the nozzle and the nozzle itself more 3-dimensional as they are snapped to a flat plane as well.
Even if your canvas is flat, it doesn't mean the things in your illustration should all be in the same plane as the canvas, so use the Z axis!
