This is old news, but I'll post some things just in case people weren't totally aware.
BioWare made the decision of letting the fans choose the new default female Shepard for Mass Effect 3.
A blonde character with a medium-length hairstyle won, but there were some who were very unhappy about her being blonde. They had a revote featuring that hairstyle with different colors, blonde, red, brown, and I think black.
Red ended up winning, so the new default female Shepard for Mass Effect 3 is red-haired with medium length hair.
Here's an announcement about it from PAX '11:
PAX 2011: Meet Your New Default Female Shepard in Mass Effect 3 | GameFront
In the media section of the official Mass Effect site, there are some full-size backgrounds of her:
BioWare | Mass Effect | Media : Wallpapers
The image in that gallery titled Fan Artist Shepard was done by the fan artist Patryk "Garrett" Olejniczak, who was hired by BioWare after the SDCC fan art contest (in case you didn't know).