.x-icon-logout {
    background-image: url("../images/user-logout.png") !important;
}

.x-icon-Expand {
    background-image: url("../images/tree-expand-32x32.png") !important;
}

.x-icon-Collapse {
    background-image: url("../images/tree-collapse-32x32.png") !important;
}