i had some extra hats in my backpack that i didn't want to sell. then i figured out there was a hat stand! so i bought them and i figured out you cant put your own hat on there! so i wasted crowns. It should either say you cant put your own hat on the stand, or just make it able to.
There are male and female mannequins that you can craft from Felicia Worthington in Regent's Square, in Marleybone, and you can put any extra hat, robe, and boots you like on the mannequin!