.awesome-footnotes-admin-button {
    background: url(../assets/icon.svg) 3px 5px no-repeat !important;
    background-size: 20px !important;
    display: block;
    width: 30px;
    height: 30px;
    padding: 5px;
}

.mce-i-awesome-footnotes-admin-button {
	background: url(../assets/icon.svg) 0px 0px no-repeat !important;
    background-size: 20px !important;
}