border-image, background, linear-gradientを指定したサンプル

h1 {
  border-width: 10px;
  border-style: solid;
  border-image: url(https://iwb.jp/ss/iwbjp.png);
  background: pink;
  background-image: linear-gradient(to right, #1e5799 0%,#2989d8 50%,#7db9e8 100%);
  color: #fff;
  text-align: center;
}