This. Either at the beginning of the game or sometime during the game.
If I'm going to make a guess, I'd say we'll get to do it during the process of importing the world state from the Keep and into the game.
For the last several playthroughs, I've been using the default Hawke appearance, sans the ketchup, and since I have too many playthroughs to have one that's "my official," or even several, I think I'm going to be perfectly fine with the default Hawke.
Obviously, for those who modded Hawke's appearance, it will be different, since it's highly unlikely that you can import the modding resources.
I also must say, with my numerous playthroughs in mind, I am getting more and more used to the idea of importing a world state, instead of a specific save game, and I was positive to it from the start. I hope the Mass Effect team picks up on this.