Yes. I suggest you don't stick so much to straight ramps with just a variation of lightness going across them. Introduce complementary color shifts and subtle tints. Also you don't need so many colors for so small pieces of art. Clarity is more important than smoothness. I wouldn't actually suggest more than 8 colors for these.
Grey is not a good color for playable character ships, attempt more vibrant stuff so they don't get lost in a shooter environment.
Good luck with your project.