Here are my two cents: (sorry for my late reply, I had issues with my keyboard which basically stopped working for almost a day for no apparent reason
-If Superstructure shading for forward and aft facing surfaces is implemented, light should always come from the bow. A possible variant of this is implemented in Colosseum's drawings, and shows the shades on the back of curved surfaces only.
-Superstructure breaks or bends drawn in black for 90-degree breaks, dark grey for angular breaks, no darker bends on curved objects.
-Curved/Cylindrical objects are shaded with a small stripe of lighter shade, wider stripe of basic shade and another narrow stripe of darker shade. Both lighter and darker shades are relative to the object shape, but usually the basic shade section should be bigger than the other two (A method I've always used on my ships). Another technique is that used by Gollevainen and Heuhen, with the lighter curved surface represented by using two single-pixel stripes of lighter shade to give the "illusion" of reflected light.
-All platforms supposed to be walkable should be three-pixel thick (with maybe a few borderline exceptions in order to avoid the two-black-lines issues and pixel blobs).
-Keep using standard railings as it has been always done.
-Underwater hull in red, unless it is known to be in some other color.
-Proper hull shading used if the gereal shape is known, even better (and somewhat required) if the artist has body plans to work with.
All arguments have pretty much been mentioned already by some other users, but I wanted to share my thoughts on the matter.