When I attempt to add a background wallpaper to my Mac from my list of Albums from my Photos App, they are all empty?

Are you doing this from the "Desktop & Screen Saver" "System Preferences" pane? Here is a screenshot of my "Desktop & Screen Saver":

Does the Photos application show the pictures you expect OK?

Do you have your photos in a non-standard location (should be in your home folder in a folder called Pictures in a file called "Photos Library.photoslibrary") or do you have multiple photo libraries?

Do you have the latest update to Sierra, i.e. 10.12.2?

Good luck...

Have you set your Photos library as the System Photo Library?

In Photos click on Preferences under the Photos menu bar item.

In the General pane of Preferences you will see Library Location

and two buttons Show in Finder and Use as System Photo Library.

If the path to your photos library is correct and the Use as System Photo Library

is not greyed out please press it now.

Relaunch System Preferences and go to Desktop & Screensaver>Desktop.

Hopefully you should now be able to select from your Photos, Moments and Albums etc now.

Try restarting in Safe Mode, then restart normally

Follow these steps to start up into safe mode.

Start or restart your Mac.

Immediately after you hear the startup sound, press and hold the Shift key.

Release the Shift key when you see the Apple logo appear on the screen.