I had a default face Shepard (I got exceedingly frustrated at facial construction) buuuut here goes!
Nathaniel Shephard, Soldier, Earthborn, War-hero.
Personality wise, he is a fairly straight-edge and recognizes the need of regulations and rules, but also understands that there are a few moments when one needs to be assertive--moments when regulations and code do not give guidelines that explain how or what choices to make that are in the best interest of the mission, or the people you are trying to protect.
He romanced Tali, survived the suicide mission with everyone at the collector base. He convinced Wrex that Saren's "cure" of the genophage was not the cure Wrex wants and unwillingly sacrificed Ashley during the Virmire mission, and saved the council in the push against Sovereign on the citadel, realizing the Council needed to be saved if there was to be any chance of an alliance powerful enough to stop the likes of Sovereign.
In ME3 Nathaniel had united the Turians and Krogan, and cured the Genophage--and even oversaw the smoothing over of relations with Primarch Victus' son on Tuchanka by disarming a bomb that could potentially wipe out the Krogan--both by massive casualties, and by starting a war between the newly formed allies.
On Rannoch, the Commander had united the Geth and Quarians. Ending a centuries-old, bitter conflict and restoring hope for the Quarians all while making Tali's dream for a house on her homeworld, a reality.
Thane had been killed by Kai Leng, and Shephard mercilessly shattered the assassins sword and took special pleasure in taking the assassins life, especially since the Commander felt that he had failed in protecting a close friend and a good man.
song:
www.youtube.com/watch (Black Hawk Down OST: No Man Left Behind)