I did not install the addon from emanuele, because there is still something wrong in my forum.
But it works without this addon. I am using the light-Theme.
You need six icons, they have to be uploaded in "images /_light".
Then there are some changes in the index_light.css
It should look like this:
.category_boards .board_icon, .board_key:before {
background-repeat: no-repeat;
/*background-image: url(../../images/_light/board_icons.png);*/
}
/*.on_board {background-position: 0 0;}*/
.on_board {background-image: url(../../images/_light/on.png);}
/*.on2_board {background-position: -72px 0;}*/
.on2_board {background-image: url(../../images/_light/on2.png);}
/*.off_board {background-position: -144px 0;}*/
.off_board {background-image: url(../../images/_light/off.png);}
/*.redirect_board {background-position: -216px 0;}*/
.redirect_board {background-image: url(../../images/_light/redirect.png);}
/*.new_some_board:before {background-position: -300px -14px;}*/
.new_some_board:before {background-image: url(../../images/_light/new_some.png);}
/*.new_none_board:before {background-position: -372px -14px;}*/
.new_none_board:before {background-image: url(../../images/_light/new_none.png);}
/*.new_redirect_board:before {background-position: -444px -14px;}*/
.new_redirect_board:before {background-image: url(../../images/_light/new_redirect.png);}