Tool > Geometry > Divide.
You might want to read about this subject, since it´s essential to understand what you´re doing.
im far from expert too but these are my suggestions and my paintover:
1. Format - Your 800x600 format feels awkward to me, Id stretch it out to be more of a cinematic format.
2. composition - i...
Don't use so much black / white for shadowing and highlighting. Also, things in real life do not have outlines.
Rule number 1, you do not talk about Conceptart.
Rule number 2, no outlines in real life. Having the sword/dagger outlined will achieve the exact opposite of real, it also stands out because...
One of the techniques for realism is to add a depth of field/depth of vision to your image.
When we look at an object close up, the stuff in the background gets blurrier.