.transparent-grid {
    background-image:
        linear-gradient(45deg, #ccc 25%, transparent 25%),
        linear-gradient(-45deg, #ccc 25%, transparent 25%),
        linear-gradient(45deg, transparent 75%, #ccc 75%),
        linear-gradient(-45deg, transparent 75%, #ccc 75%);
    background-size: 20px 20px;
    background-position: 0 0, 0 10px, 10px -10px, -10px 0px;
}

有 src，透明部分是方格图

没有就是整体都是方格图

  <img className="transparent-grid"  key={index} id="img" src={item.src}                          
                            }}/>