I bought a mod that done this, and found the mod took longer to work out than coding myself. I use this code.
Here you have unread and read. Just repeat the code for each node in your extra.less template.
Change the X to ID of your forum and of-course the image.
Code:
/* 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 */
If you just want to change the read and unread default XF2 nodes to 1 image.
Code:
/**********/
.node .node-icon i { display: none; }
.node .node-icon {
background-image: url('/images/yourpic.png');
background-repeat: no-repeat;
background-position: center;
}
.node--forum.node--read .node-icon {
background-image: url('/images/yourpic.png');
background-repeat: no-repeat;
background-position: center;
opacity: 0.4;
}
/**********/