A Mannequin is a Furnishing with 28 Storage slots and which can be "dressed up" with Armor kept in storage. It resembles any one of the 5 races, and both genders, and can be posed after completing certain prerequisites.
Specific Mannequin Models:
How to Obtain
Upon completion of the Knocking on Forbidden Doors quest, Fyi Chalmwoh will offer to pose Mannequins at the cost of 200 gil per pose change. You do not need to remove the mannequin from your mog house to change its pose.