sweet. I never was a fan of shinobi, probably because I was boobooo when that game came out. But I like the whole style (which i think Raven from Tekken 5 totally ripped off).
And excelent work on this =]
Personally, I'm loving the greyscale. It's suits your style well, I think. Also, the character is really intriguing, I'm very curious about him! (I'm really digging his facial hair/beard. Just thought I'd throw that in there.)