Tried some shading. Thoughts?
1. Bridge and turret slots need shading.
Bridge should be elavated and I recommend lowering the weapon slots a bit.
Vanila starsector shading is done with a light source in upper front of the ship. Which means the slope facing bow is brighter, while the one facing aft is darker. Those facing starboard and port, if in same degree, have same brightness.
2. Engine could be better with some work.
The dark slopes facing aft are meant to be propulsions, right? I recommend, unless you have a solid concept about how your ship's propulsion will look, to stick with vanila propulsion design. It's not that hard.
( Hint: They're basically iron pipes

)
That is not to say to change the entire design concept. Just the engine part.
3. Turrets might overlap.
Make sure you keep enough distance between turrets. They might overlap one another when weapons are installed.
Hopefully, somebody else will advise about greebling. I'd just say to look at some vanila sprites.
You must have noticed me saying to follow vanila stuff over and over. Since your sprites are meant to be used in a game, it is important to blend naturally with the ones already exists.
Overall hull design is not mine to judge. I won't say it is too boxy, or anything. It's up to you and looks fine.
And as Sproginator said, nice start!