Does Mirror Image stack with other effects, like blur or displacement?
Although this is referring to your attacker being blind, the Mirror Image spell provides a clue.
Mirror Image:
"...although normal miss chances apply"
I think it points out that "normal miss chances apply" in the case of blindness, and other affects. So, I would say yes.
But both Displacement and Blur provide miss chances (50% and 20%, respectively), so I don't know if they would stack. The last section of the Concealment portion (page 197 of the Core book) says that "Certain situations may provide more or less than typical concealment, and modify the miss chance accordingly."
I take that to mean that the GM could play it either 50% (the max), 70% (stacking), or maybe some middle-ground, such as 60%.
Miss chances don't stack the greater one applies. I can't remember if that is a 3.5 ruling or a pathfinder ruling, but either way it is still relevant.