This is actually pretty simple:
old method
.logo-big {
display: block;
-moz-box-sizing: border-box;
box-sizing: border-box;
background: url(awesome-dark-logo.png) no-repeat;
width: 150px;
height: 40px;
padding-left: 150px;
background-size: 150px 40px;
}
You basically evict the existing image out of the IMG tag