Thanks everyone!
I've been doings some more concepting. These are quite quickly drawn and do not contain much detail. The back view is missing her hair to show the amour beneath.
Top left has some more detailed concepts for the shoulder armours.

@rgdraw Thanks
Concepting the various armour and clothing pieces. Next up will probably be colour testing.

Here is the first color test with flat colours. I am truly a beginner in colouring, so I could use every bit of help I can get
The idea is to make the armour look like it has been burned by fire. Either that, or silvery.

@rgdraw Great! Still not sure if I should change the blue cloth into orange.
Second colour test with a lighter armour and an orange tabard.

And some ideas for a pose in the final illustration. I have two options: a fighting stance, or a calm one. For a fighting stance, the mask will be lowered. For a calm one, it will be up.

Currently leaning towards a calm pose, #8.

@rgdraw Thanks! Yes, I think I will go with the darker armour. It works better with my plan.
@HorizonDweller Thanks!
Decided to refine the lineart, still a work in progress.

@rgdraw Thanks!
Actually, I'm out of ideas for the background. Currently thinking something about a setting sun / battlefield, but I'm open to any suggestions.

@rgdraw That's pretty much what I had in mind
More lineart, pretty much finished with it. Next, colouring...

@rgdraw I am not very good with colours, so I am always dreading this phase.
Not much progress today, just painting the flats.

So I fell terribly ill and thus have had not much time to work on this. Still feeling a bit feverish, but I hope I can finish this in time. Still have to do highlighting, armour and finished the shadowing.

@rgdraw Yes, feeling fine and dandy
Progress for the moment, still need to highlight the rest of the armour and do detailing for the tabards. And the background. And the overall lighting.

And for a bonus, the current shadows (thought it looked cool).