.bookmark-item[container="true"] {
list-style-image: url("file://C:/Temp/folder_closed.png") !important;
-moz-image-region: rect(0px, 16px, 16px, 0px) !important;
}
.bookmark-item[open="true"],
.bookmark-item[container="true"][open="true"] {
list-style-image: url("file://C:/Temp/folder_open.png") !important;
-moz-image-region: rect(0px, 16px, 16px, 0px) !important;
}

treechildren::-moz-tree-image(Name, container) {
list-style-image: url("file://C:/Temp/folder_closed.png") !important;
-moz-image-region: rect(0px, 16px, 16px, 0px) !important;
}

treechildren::-moz-tree-image(Name, open) {
list-style-image: url("file://C:/Temp/folder_open.png") !important;
-moz-image-region: rect(0px, 16px, 16px, 0px) !important;
}