MacBook Pro-Change Background doesn't display/use all of the jpg pictures in the folder
OK - I figured it out.     You have to click the FOLDER under its root when you add it to the Desktop &amp; Screen Saver folder with "+" 

For example.....if the folder is ....Documents\Backgrounds\winter(jpg files) --- you have to select the folder under ....\Documents\Backgrounds (select Winter)

I selected it under the actual directory ...\Documents\Backgrounds\Winter all of the jpg files displaying and selected "Winter" at the top.   (Need to select one directory back)