Ok. Well. Just now I still learn and practise. And I listen your advices and waiting for others. And then i would make "great ships"... Just help me with advices...
I'm rather new myself so I can't really help much but I do know a couple things:
1) Try to shade different colors to help with the effect of 3D. You can take a look at my ships in my sig and you can see a bit of definition because of color (not a whole lot, because again, I'm new myself). Use darker colors like dark gray for lower sections and use light gray or white for higher sections. Easy trick to help with depth.
2) Other than that, just remember to alpha 0 your modules and your thrusters, and be sure to not overload your ships with weapons. A few bigger guns are much better than 40-50 blasters.
That's about all I can help you with, good luck in the future