open/close Icon in Accordeon

I’m using theme “clouds” and wold like to change the accordion open/close icon. As i found out with the dom inspector, there are png files used for that.

how can i change them and use fontawesome icons for the accordion instead?

You can check the styling in “flat” skin, and add the similar one

.webix_accordionitem .webix_accordionitem_header .webix_accordionitem_button {
    color: #fff;
    background-image: none;
    font-family: FontAwesome;
    font-size: 24px;
    text-align: center;
    width: 24px;
    height: 45px;
    margin: 0 10.5px 0 10.5px;
.webix_accordionitem.vertical>.webix_accordionitem_header.collapsed .webix_accordionitem_button:before {
    content: '\\f107';
.webix_accordionitem.vertical>.webix_accordionitem_header .webix_accordionitem_button:before {
    content: '\\f106';

.webix_accordionitem .webix_accordionitem_header.collapsed .webix_accordionitem_button:before {
    content: '\\f106';
.webix_accordionitem .webix_accordionitem_header .webix_accordionitem_button:before {
    content: '\\f104';

First class assigns FontAwesome to the node, others define glyphs for different states