From what I undestand, scent lets you pinpoint the square’s direction a creature occupies.
Scent reads, in part:
The creature detects another creature’s presence but not its specific location. Noting the direction of the scent is a move action. If it moves within 5 feet of the scent’s source, the creature can pinpoint that source.
What happens when someone is under the Mirror Image‘s effect and gets attacked by a creature with scent? Does this extraordinary ability let you spot the real target between all the figments?