What is the ruling on using a "hair mannequin," which is essentially a sculpted head and hair only, with the possibility of covering the obvious facial features?

An image that is incomplete in its creation, meaning it lacks something essential for life, such as a chest or a head, is not prohibited according to the majority of scholars. There is no objection to possessing or using it. This includes figurines that were originally made in a truncated form, or those that were depicted complete but then had a part removed without which life cannot persist, whether they are erected or not. This is based on the saying of Gabriel to the Prophet, peace and blessings be upon him: "Order the head of the idol to be cut off so that it becomes like the form of a tree." It is not sufficient to remove the eyes, eyebrows, hands, or legs; rather, the missing limb must be something without which life cannot endure, such as cutting off the head, obliterating the face, or piercing the chest or abdomen.