.glyphicon-plus:before
{
    background-image: url('../image/carpeta.png');
    background-size: 20px 20px;
    display: inline-block;
    width: 20px; 
    height: 20px;
    content:"";
}
.glyphicon-minus:before
{
    background-image: url('../image/carpeta-abierta.png');
    background-size: 20px 20px;
    display: inline-block;
    width: 20px; 
    height: 20px;
    content:"";
}
.glyphicon-tree-conifer:before {
  content: "\e199";
}
.glyphicon-tree-deciduous:before {
  content: "\e200";
}