I came across a bizarre instance where a Pact Blade Warlock with the Witch Sight invocation ended up fighting several lower-level mages, a few of which cast Mirror Image. The Warlock claimed that Witch Sight saw through these false images so that he could see the true mages only.
The Mirror Image spell says:
A creature is unaffected by this spell if it can’t see, if it relies on senses other than sight, such as blindsight, or if it can perceive illusions as false, as with truesight.
The Witch Sight eldritch invocation says:
You can see the true form of any shapechanger or creature concealed by illusion or transmutation magic while the creature is within 30 feet of you and within line of sight.
As the mages are not technically concealing themselves with Mirror Image, I am unsure whether Witch Sight can see through the illusory images, as it only shows you the "true form" of the creature or shapechanger "concealed" by illusion.