Out of all of them I think that the one labeled 'a' is the best. To me, 'b' seems to have the brightness set too high and it somewhat hurts my eyes to look at. 'c' is okay, it just has less flow as 'a'.
One thing you could work on is blending. It would look 100x better if the person in the sig was blended in a bit more. Overall though, it's pretty decent. I'mm interested in seeing other graphics of yours.