(now that I've read this thread more closely
The problem with ryuk is that he is often stylized quite a bit different, especially in the color photos. As I interpret it, the shirt is not his skin, but instead a loose shirt that he clumsily stapled/nailed onto his flesh to keep it from falling down, like suspenders.
Sometimes he's grey, sometimes he's white, sometimes he's blue, sometimes he's purple. His clothing varies in color from black to blue to burgundy, likewise with his hair. I'm planning to go black with red highlights for the clothing, hair and feathers, and a blue-gray for the skin.
I've got no clue what I'm going to do to get that ragged look on the sleeves. and I'm having a heck of a time finding something to do for the wig.
Now that the anime has come out, there are many new and very nice reference photos. If you haven't checked it out yet, you should absolutely do so.
I've got a page of reference photos for my personal needs here