On the poster for the 2013 Carrie, only one side of Carrie's face is covered in blood. The other side has a few spots but it otherwise clean. This shows Carrie's morals and possibly sanity.
One side is all dark and red, showing the goodness and sanity inside her, but the other side is slowly getting redder and redder with blood, showing how she is slowly tipping into the dark side. This could be the other way around, with the red representing her lack of sanity but her still having a few spots of sanity, along with morals.
Loads of people have probably pointed this out but I thought it was cool.
