Really nice, like previously stated, so I'll skip the formalities. I do arching, and that arrow doesn't have contact with the string. You'd use the 2 fingers that the arrow is between to pull the string, never the whole hand, like it looks as if he does. Actually it almost looks like the string is pulled with his mind alone and a forcefield between the string and the arrow will propel it.
The arrow should technically also be rested on the thumb/index finger (I hope that's correct, English isn't my main language) as you'd otherwise risk ripping the hand open with the feathering, or at least messing up the flight path of the arrow when it's fired, but that's aesthetically not such a biggie, and I didn't notice that at first, and mostly, other people don't either, so that one's minor I think.
You're really great at expressions and giving life to the characters you paint, and your technique and human fluidity in poses is exceptional, just thought I'd add that, because I really do think that's something you do extraordinairily well, and I wish some other 'professionals' would learn to do that as well.
The painting is lovely; all the little details (wrappings on the bow, metal bits on his belts, the sigils over his eyes allowing him to "see," the detailing on his armour) make this a very pleasing image.
One little detail, though, slipped past I think... This poor guy is going to have a massive welt on his left arm from the bowstring because he doesn't have a vambrace; he has one on the other arm, but archers usually wear one on the arm that holds the bow because the string slaps the arm when it is released, and it _hurts_.
Of course, it could just be that elves are too macho to notice pain