Use TabCapture

Add script bellow to your bookmarkbar:

 javascript:(function(d){var b=prompt("Image Link", "https://example.com/bg.png");var e=d.createElement("div");e.style.cssText="width:100%;height:100%;position:fixed;left:0;top:0;z-index:2147483647;background:url("+b+");opacity:0.1;";var v=d.getElementsByClassName("html5-video-container")[0];v.appendChild(e);})(document);