OK, put the image in a folder and changed the style code to this:
<style>body {background-image:url("images/levitating_maus.jpg");}</style>
and it works.
However, when I move the CSS to an external stylesheet located in the root, the image doesn't show...
HTML:
<!DOCTYPE html><html><head><link rel="stylesheet" type="text/css" href="mystyle.css"></head><body><h1>Hello World!</h1></body></html>
External CSS:
<style>body {background-image:url("images/levitating_maus.jpg");}</style>
Thanks for looking...