I don't want to go picky again.. but..
If C&C wanted, here I come.
First of all Mother Anathomy is in the works. Really, get some reference pictures, you don't seem to be using them.. In example (random google find)
this one. Check the abdomen looks. Where the front torso muscles end, they don't extend to the armpit. After all, the muscles are positioned on
bones. They somehow limit the possibility of muscle shape.
This one might not be the perfect example, but it shows how the neck-to-arm muscle is build, and it cannot go making a extra hill. Classic
Nomura art is the perfect one to check the face and just grid it and try to fit the shape/sizes. There is no "bulge" between the eyebrows/topnose unless you hit yourself real hard. And
this artwork (which I must say is one of the best Sephiroth fanarts I have seen) shows the neck muscles. The parts that are exposed should be ligther, and it's majorly a tendon. Check the ear size. He looks really old.
/rant1 end
Some basic I help I can whip up in limited time, other then that I am impressed by your skills, they indeed went up.. but 3d modelling without basic knowledge of human anathomy, or reference is really a hardcore experience. Use a mirror, search the net, for every artist it's a grave difference.
I'm pretty sure that the vision of Sephiroth mine and yours differ like ant and lion. I see him as the slender, fast-bladed ultimate-bishounen, you seem to do the muscled insane killer. So there will always be scissions between our views.
Good luck~!