Cached background-image in style.css

Ok this is more of an html/css question as opposed to a Blocs question, but I am stumped so thought I’d try here first.

I have a custom class in “style.css”:

background-size: contain;
background-repeat: no-repeat;

This style class is applied to a transparent graphic on one of my pages. What “loadTeeCam.php” does is walk the image files in a single directory, deleting all but the most recently created, and returns the image data of that most recent image.

This all worked well when I implemented it several years ago, but in more recent browsers the background image is cached so solidly that it is rarely refreshed. Used to be I could do a simple browser refresh and have the “loadTeeCam.php” run and refresh the image. That seems to be no longer the case with a client side refresh, but a server side refresh does run loadTeeCam.php and update the BG grc.

So how can I prevent the background-image of the image that has this style class assigned from being cached?

Any help appreciated,