There is plenty of documetary evidence Jesus existed. The Romans felt he was a political agitator, the pharasies though he was blaspheming, as for his appearance - he was from that region. He would look like the Arabic stock we see now. Isreal has had the influx of European migrants so they are more ethnically mixed but something like them too.

Length of hair? Dunno - fashions change - maybe he would not look like his contempories - in order to stand out. Clothes - simple, cheap and practical, coarse weave cloth.

But how would a Devout Atheist like me know?