/* Node icons */
.node--idX .node-icon i { display: none; }
.node--idX .node-icon {
background-image: url('/images/yourimage.png');
background-repeat: no-repeat;
background-position: center;   
}
.node--forum.node--idX.node--read .node-icon {
background-image: url('/images/yourimage.png');
background-repeat: no-repeat;
background-position: center;
opacity: 0.4;
}
/* Node icons End */