title: Forcing refresh of a background image
body: <p>Is there a way to make sure that a certain background image recently updated does appear in its last version on everybody's browser (rather than the old version stored in cache)? </p>
  
  <p>It has to be a solution not involving touching the line of code calling the CSS (I could put a question mark and a version number after the css file name, like : <code>&lt;link href="styles.css?v=2" rel="stylesheet" type="text/css"/&gt;</code>, but in this case I don't have access to this part of the code)</p>