I'd also add that, if you'll notice, the background of this forum (Which is from a wallpaper.) also looks like the same character, and the character in the trailer also looks like the same one, so aside from this character being one of the developers' characters, he also seems to be they're main promotional character. In Oblivion too, I don't recall seeing many pre-release screenshots showing a player character who was not a male Imperial, and while I wasn't around in time to follow Morrowind's development, I'm going to go ahead and assume in pre-release screenshots, the player character was also usually a Dunmer. And why not? For the main promotional character, Bethesda probably wanted someone who would best sum up the feel they were going for, because obviously, they can't show screenshots of every single character players' could possibly make, so instead, Bethesda probably decided to go with the first thing they thought of when thinking about the hero of Skyrim, and I guess that was the character we've seen.
Though I don't really need to see screenshots of a Dragonborn of other races or sixes, myself, just knowing we can play those other races or a female character satisfies me, now, seeing characters of other races would be nice, just so we can know what they look like, but they don't need to be the player character, they can be NPCs too, as long as they're not Nords.