list-style-image size
li{
list-style: none;
}
li:before{
content: '';
display: inline-block;
height: 20px;
width: 25px;
background-image: url();
margin-right:5px;
}
css list style url siz
li{
list-style: none;
}
li:before{
content: '';
display: inline-block;
height: y;
width: x;
background-image: url();
}
Source: stackoverflow.com