Установка картинки png на элемент

a { 
color:#fff; 
font-family:sans-serif; 
display:inline-block; 
background-image: url(https://i.stack.imgur.com/KAzh4.png); 
background-position:center; 
background-size:100%; 
padding:40px; 
}

<a>Скачать</a>

button { 
  background: url(//i.stack.imgur.com/KAzh4.png) center; 
} 
 
.large { 
  height: 1080px; 
  width: 1080px; 
  border-radius: 50%; 
  font-size: 128px; 
}

<button>Кнопка</button> 
<br> 
<button class=large>Кнопка</button>