For macOS Sierra I am trying to change the login image. I am going to System Preferences → Users & Groups and clicking on the edit button on the image.
An image selection popup appears. I have to add an image to any of the location so that I can select that images (I downloaded from internet) but none of the location is accessible.
There are locations like "Photo Booth" "iPhoto" "Photos" etc but I couldn't find the location where I can copy my newly downloaded picture.