I have been trying to add my own pictures to the backgrounds in f28.

After opening the settings window , select background, and click the background item
I get another window with Wallpapers, Pictures and Colors.
Upon selecting Pictures there is a msg no pictures found and a link to the Home
folder is shown. I added a bunch of photos to the pictures folder but there
is no clear way to select a single photo or all photos.

I see there is an xml file in /usr/share/backgrounds/f28/extras/
with a list of each photo in the folder. Is editing this file necessary?