Talent image approvals (also called cast clearances) are contractual rights that let an actor control which photographs of them a production may release. Most cast contracts grant kill rights: the ability to veto (“kill”) a set percentage of their images, protecting their likeness and brand.
Terms vary by actor, but a common arrangement is the right to kill up to 50% of solo shots and 25% of group shots. Managing those percentages by hand, across a full cast and thousands of unit stills, is where productions get into trouble. The approval process exists to make it fair, auditable and fast.