.block-ti-tree li {
  list-style-type: none;
}
.block-ti-tree li::before {
  padding-right: 1ex;
  content: url("../img/folder.gif");
}
.block-ti-tree li.open::before {
  content: url("../img/folderopen.gif");
}
.block-ti-tree li.organizational-leaf::before {
  content: url("../img/page.gif");
}