Upon close inspection, the man has Blond hair. So it can't be Shirou/Archer. I can only guess it'd be Gilgamesh but then again Saber wouldn't be happy about that.
So, with that said... random man? Even though it looks like official series art.
watsonsan said: Did you forgot the main point of any eroge? They never show us main hero's face, it's belivied the hero is you. ^__^
Not in Fate/Stay Night. At several points in the game, the art clearly shows Shirou's face and most of his body.
Also, not enough of the man's hair is visible to pin down an identity; what is visible of the hair color could be being distorted by the lighting. For all we know, it could be Archer.
Considering that Shirou eventually turns into Archer, you can assume that's Shirou based on his structure. IIRC, Archer got white hair and tanned skin from his constant stress and battles. This could be Shirou without that.