I have always struggled with desktop backgrounds. One way it's oh-so-cool to have a nice, colorful or cool image as your background. On the other hand, it couldn't be more useless. At least when working in Windows you have windows maximized and you rarely see desktop at all. So what's the point?
But the other day I came across a nice peace of software that let's you have a image of earth right there on the desktop. It's called DesktopEarth, free and lightweight. It will create composite desktop images of earth. Complete with night and day shading and "live" clouds.
So when you wonder how the weather is going to be tomorrow, just hit Win + D and see for yourself!
It even understands multiple monitor configurations as you can see on this screenshot of a desktop on my work machine.