Alrighty, starting to get there I think:
Really cool design and rendering. I think use of colour is holding it back -- not the bold colour choices, that's awesome and distinctive and I'm a big fan, but rather how those colours are applied across a range of shading.
Take the darks in the image; they almost look like they have a red fog covering them. The shadows are almost the same hue and saturation as the highlights, the only real difference is luminosity (and the luminosity range is a bit conservative). This makes the rendering look more flat than it should and makes the various sections of the ship look disconnected.
To show what I mean, I did a subtle adjustment and compared various qualities of the colour ramps:
So I adjusted the hue range there to be cooler, less saturated, and darker in the darks. The highlights are a little brighter, too, and there was a paltry and token attempt to adjust the other colours. This is just to show what a subtle change does; I think you could push it a lot further.
One way to think of this is given that the colour of light affects what colour an object appears to be, the entire ship should appear as though it's in the same lighting condition as the rest of the ship. In most photographs we're used to seeing, in very rough terms shadows are a little bluer, highlights a bit.. well, washed out sometimes, but that depends on the material and environment. Anyway, similar rules can apply to the ship to make it look more unified -- bluer shadows that tint (but don't dominate) all of the dark parts, regardless of colour, and maybe the highlights get washed out a bit and shifted toward some overall mood-colour (in base ships, blueish for high-tech, sepia for mid-tech, rust for low-tech. Or thereabouts.)
Or the shadows can be warmer than highlights; what matters is that there is a consistent shift in hue, saturation, AND luminosity. Making that shift go toward a colour complementary to the most commonly used colours in a design just makes that contrast stand out more strongly.