There are instructions on the image FAQ page, but you do it by clicking on the image then scroll down until you see People & Things in the Image: and you will find a REMOVE option. Select that and save. The image won't show up on the profile anymore and will eventually be removed. It isn't removed immediately in case you made a mistake. Also, the FAQ can be found at a link in the upper right hand part of the page that comes up when you click on the image.
