First of all, thanks for the help pistachio.

Now that I look at mine again I can see the pillow-shading and banding. Especially the pillow shading on top of the ships, although that's not what I was intending it to look like, I just have problems picking highly contrasting colours together sometimes for some reason.

I prefer the angular appearance on the top of your first ship, I might try to achieve something like that in the next version.

I shied away from using an obvious light source as I'm doing rotation on the fly if I need it for the game I'm making these for, and would rather not have to draw each facing.

I'm generally aiming for a cartoony look, ideally something like these screens below from Tatsujin Ou/Truxton 2:



or another Toaplan game I like called Dogyuun:



Although I realise I won't reach this standard, at least in the time I plan to finish these sprites