代码如下

将下面代码放到子比主题后台=>>自定义CSS里面即可

/*仿哔哩哔哩弹窗背景*/
.payvip-modal {
  background-image: url(https://img.alicdn.com/imgextra/i1/2210123621994/O1CN01zWJtdh1QbIhbcKakX_!!2210123621994.png),url(https://img.alicdn.com/imgextra/i3/2210123621994/O1CN01nUULwt1QbIhdvLeL7_!!2210123621994.png);
  background-position: 0 100%,100% 100%;
  background-repeat: no-repeat,no-repeat;
  background-size: 20%;
}