The above was achieved with nothing but the actual game, and MS paint.
You can find the sprites (images) of the game's ships under:
Fractal Softworks/Starfarer/starfarer-core/graphics/ships
You can then open up a ship with a program like MS Paint. Then you can cut away parts that you want to use, and build your own "template" as it were. Then use those pieces to cut and paste until you have a ship.
WARNING! Be sure to copy the image first, or create some sort of backup.
Now for a quality result, you'll probably want graphics software with a few more features than MS Paint. The result can differ quite a bit:
A good (free) choice would be Gimp.