Don’t know. Was given the option to choose random images in the Custom Header link (Appearance -> Header). Uploaded the images and chose the Random Image variation instead of single image. One of the images doesn’t fit, so tried to remove it. No chance. The only way out of this that I can think of is to kill the child theme and start over. Even when you remove the images themselves, the theme doesn’t forget about them. Shows blanks where there should be images.