These show a lot of potential! Magnhildr (the one you didn't like) is actually
fucking fantastic. All it needs is a bit of polish. The mechanical wings go
extremely well with the beak-like helmet and the tail-like waist equipment. The first step is to remove those feathers and go straight
mecha-harpy by adding an additional pair of the "feathers of strength" to the wings to branch out (see spoiler for picture).
Now. Go to Colors/Patterns,
Select All, and pick something. Dick around here a bit, but if you don't know what primary color to start with, go with grey-blue. Next, pick a secondary color (like white) and turn some shit into that. You could highlight the cyborg aspect by making her skin a separate color from the mechanized parts. Now pick an "accent" color, like gold, to use only for the fine details like jewelry. Rebalance, slap on some bump-mapping. Masterpiece. If you're stumped or just lazy, send me the formula, and I'll post an example.
Durga and Kanker are also excellent, but in need of some adjustments. Let me know if you want me to go in depth with any of your other characters.
As for how you make a female ninja/kunoichi? You can start by imagining (preferably drawing) some defining feature. Think Ezio's pointed hood. You can also start with some sort of symbol/motif. Think "flower" for Leixia and "wolf" for ZWEI. You already know this stuff anyways, but if you post a rough draft of your kunoichi, I can go in more detail.