I think I made a mistake in that code, the URL shouldn't have quotes around it because Neospring does weird proxying/caching things with it. Also make sure there isn't any interfering code that removes borders

and yes the image was actually used in my trade rentry i linked it so maybe it helps u understand how i used it there

actually that's perfect because I can just give you the CSS that's used there:

.render-metadata .entry-text {
  border-color: #F0B4B3;
  border-width: 5px;
  border-style: double;
  border-radius: 10px;
  border-image-source: url(https://files.catbox.moe/0hdrox.png);
  border-image-slice: fill 40%;
  border-image-width: 30px;
  border-image-outset: 10px;
  border-image-repeat: round;
}

you can't just copy this code and use it on Neospring, because the page layout is different, but if you replace .render-metadata .entry-text with .card.shadow, .card-nest.shadow, .card-nest.shadow .card it should work