hey man, i like your illustration, and i think your right about the positives. Nice palette and pose. Good narative too.
Ive done you a paint over highlighting the things i think need addressing the most.
1, so firstly is the anatomy. At first glance i thought it was a dude, then i saw the chicks face and i was confused. Ive decreased the size of the limbs because they looked abit too pumped up for a woman, especially in the arms and legs. The armour seems abit random at the mo too. Ive not really addressed that here but it might be worth doing a few armour design studies and material studies to help you get a better idea of the design your looking for. Only thing i pushed was the helmet trying to make her silhouette more impressive, because the downward feathers on her helmet make her look vunerable, which is weird seeing as shes just killed a demon and a dragon.
2, is you composition. I think you perspective is abit off but its not so bad that it's breaking the image. The main problem that your areas of focus are built in squares (which make boring compositions.) and paralleles. Try using more angles rather than horizontals and verticals and avoid squares. This is the reason ive added more space at the top of your canvas to try and break those rigid shapes.
3, And by no means least is your values. Ive done you a greyscale version to show you better what i mean. Your forms are looking flat and there is no real areas of interest because theres very little contrast. In places like the face or the monster in the background ive upped to contrast between hard and soft and light and dark to make them more noticable. Ive also ditched the lamp in the forground because it's pulling the eye away from the action. It just feels like you put that there to explain your lightsource. i also upped the dark/light contrast on stuff like the dragon wing tip, demon elbow, womans helmet to help lead the eye around the image. I would recommend having a greyscale version ready while painting to help you with your values should you need it. (Create a new layer, paint it pure back, set to colour.)
so in a nut shell, i would recommend you study up on some womens anatomy/armour and have a look at ways to push your depth and atmospheric perspective.
It's a cool image and i highly recommend you push it through to finish, becuase it has great portential.
Hope this helps buddy