<div class="box"></div>

.box {
  margin: 25px auto;
	width: 280px;
	height: 280px;
	background: black url(https://ununsplash.imgix.net/photo-1415302199888-384f752645d0?q=75&fm=jpg&s=823bdcc1b7ad955f5180efd352561016);
  background-size: cover;
	-webkit-clip-path: polygon(0% 0%, 100% 0%, 100% 75%, 75% 75%, 75% 100%, 50% 75%, 0% 75%);
clip-path: polygon(0% 0%, 100% 0%, 100% 75%, 75% 75%, 75% 100%, 50% 75%, 0% 75%);
}