QDirIterator path("/home/max/Qt/Converter-build-desktop/img");

    QMap <QString, QPixmap> map;
    QMap <QString, QPixmap>::iterator it;


    while(path.hasNext()) // get names of files and make the map
    {
        if(path.fileInfo().isFile())
        {
            map[path.fileName()] = QPixmap(path.next());
        }

    }

    for(QMap<QString, QPixmap>::iterator it = map.begin(); it != map.end(); ++it) // fill comboboxes
    {
        fromCombo->addItem(it.key());
        toCombo->addItem(it.key());
    }