Nitrogen is a straight forward application to set your wallpaper. It will however not fetch any new wallpapers like variety does. AND it will not work on Xfce.
ONLY FOR OPENBOX AND I3
In preferences you can add more folders with your personal wallpapers. They will be added to the selection.
If you are on a dual screen, you have to tell nitrogen to either go full screen (you need to use a dual screen wallpaper then) or decide to put it on screen 1 or screen 2. You can have a different wallpaper per screen.
You have also the standard settings like zoomed fill etc.
And Variety will work an all three desktop environments.
Keyboard Shortcut To Remember
Control + ALT + I