If you just want a classy, simple wallpaper, but only have access to MS Paint (this is most useful in an office,) there exists a way to create simple gradients using an image as small as nine pixels square.

1. Use the Attributes dialog to specify a very small image. Depending on the amount of colors you want to use for the gradient, you may want to add more or less, but keep the image square.
2. The pencil tool can be used to color individual pixels and fill the image. Play around with the shape and tones of the intended gradient.
3. Save the file as a .jpg.
4. Set it as your wallpaper, in stretch mode. Windows will scale the image as if it were a photograph, and smoothly blend the image.

et viola!

To download the sample image, “Right Click, Save As” this text.