Looks good. Organic shape and design, its unique enough to easily be identified as different than the stock races or ships.
Couple suggestions; (Like Iscariot recommended) clean up your silhouette, a black outline would help make it pop (not sure how well that would show on the space background though). A greater variance in color value would make it stand out more. The 'veins' (Light blue lines) on the ship would be more pronounced if you used complimentary colors. For your shadowing try to add a touch of noise. Then some small details to add more personality to the ship, pipes, grooves, notches, vents, armor plates, windows, etc. The secret to this is to "tell a story" through pieces on the ship, have an internal dialogue with yourself as you add details and make that conversation relate to the details and their purpose in the design of the ship.
Like I mentioned earlier though you have a unique look and feel to your starting image. Keep it up
A side note, when designing for pixel art figure out your final image size, then paint your target at 4 times this size. Then when your done reduce the image by a multiple of 4 and pixels will be much more crisp and blended than by any other size variation. Imagine 4 pixels in a square formation when they are averaged and dropped by 4 they will become one pixel which is the average color/hue/value of the first 4. If your in Photoshop try playing with the bicubic sharper (in image resize window) when your change the size of your image.