It seems like if the Bills don't get Lynch or Peterson, the next guy in line would be Antonio Pittman. He is smart and comes across well in interviews etc., probably doesn't hurt that is from Ohio State.
The Bills are kinda in a quandry. They need a back, but they might have some reservations about Lynch. He seems a little tight in interviews, like he is on his best behavior. I think he is probably fine "character" wise, but if the Bills blow it, that could seriously hamper the development of the team.
Pittman looks pretty good and might develop. He is a Junior. There are concerns about his size, but he could bulk up a bit, he's 5'10", the right height. The footage I have seen shows him making big runs against well blocked defenders that don't touch him until he is well past the line of scrimmage.