wow, this is a really accurate drawing of david bowie in his ''ziggy stardust'' stage, i like how you drew his eyes/face/nose/mouth, everything on his face looks VERY realistic, with some really realistic lighting/shading effects.
his eyes look really life-like; same thing is true about his mouth as well, it looks like a real mouth from a photo, and thats why this shine on his lips is such a good artistic move, its because it makes the human lips to look alot more life-like, just like we draw the eyes with a ''liquid, teary-like'' state, so that they are vivid, and liquid, just like the eyes in a real-person.
overall, his face is PERFECT, and really life-like, especially the eyes/nose/mouth parts, while his neck is realistic and has a nice shine on light on it, and his hair/facepaint look really good, and nicely drawn as well.
all in all, i have to say thats its sad to see people go, and its also sad to see pleasant, cool people and good artists like david bowie to leave this earth, so early like that.
may he rest in peace.
you did a good tribute.