This is neat maybe a little more light would have helped this photo do better but then this mood here would be totally different... I like it and it fits the challenge well..
You have an extremely interesting subject here, but I have no idea what he's doing; what the right side of his face looks like; or where he is. It appears as though you've captured some good details in his face, but there's too much negative space (the subject is too small) to see them, and I'm sure they're most definitely interesting. This image has great potential and a wonderful subject; however I feel there's so much more this image could do... creating a story, giving me an insight to who he is, what he's doing, where he is... and this image comes short there.
Seems more like a studio portrait then a candid to me. The lighting and background all seem to setup to be a snapshot in the "wild." It is a very nice portrait though. 6