Shepard's dance is iconic. Maybe there could be some gesture or pose that you could associate with the new character even with space suit and helmet on...?
And maybe they would release versions of the trailers where you can customize the main character's appearance? Maybe it would work the best after release, as a bonus content along the game.
If the default face is too interesting looking, I end up using it. This happened with male Shepard and Hawke. I bought these games intending to play them as a woman, you know. And my replays tend to be the same character with variations based on hindsight. I had fun with character creator in Inquisition though.
I don't actually mind whether the iconic looks are up to me or come along the package. The more they're able to express personality, the better. Character with known appearance comes handy with snappy fanart, at least. Though good outfit might be as effective as iconic face? In some cases?
I like how default face Shepard has slightly crazy look in his eyes (unlike his face model who looks just different person). Many custom Shepards seem more laid back. I used Sheploo as inspiration with my inquisitors, with results that improved my game (personal taste speaking, I'm not expecting to impress anyone else). Make the eyes reflect what the character feels like inside, and each scene looks fitting for them.
-Oh while I was writing(=rambling) this, an Ugly Shepard picture was posted. Good times. 