Add overlapping png to image block

Site URL: https://apricot-perch-ztc8.squarespace.com/config/design/custom-css

Site pw: sav2020

Hi all! I'm trying to add a png image to the top/overlapping of all image blocks using :before and I can't seem to crack it. The png is a piece of tape so that the images will look taped on. Any help would be appreciated!

Here's what I have so far:

.sqs-image-content img {
  overflow: visible !important; 
  
  &:before {
    content: "";
    background-image: url('https://static1.squarespace.com/static/5f0f49d01c933a6a66f74647/t/5f0f4e2aa3d2bf40a7ccd229/1594838570419/tape.png');
  }
}