You should've added the black last. You'll be cleaning up all the runover paint smudges from now on.
I'd say... try to find a dynamic view of the ship that conveys a feeling of movement and paint it from that perspective. The most important part of a painting is the composition of positive and negative space. You can be a horrible painter but if you can compose in a viewport well it'll look awesome.
Start with trying to sketch a view off the starboard bow at a 30 degree angle. Something different looking. Once you get the sketch down then pencil it into the canvas. Paint the ship, in all detail, then cover it with tape. Then do a wash of the background over the entire piece. Once you're done removed the tape and your ship will be in space. Touch up the ship with lighting and such.
I suppose the most important part is to have fun. Good luck.