It doesn't seem to be supported out of the box by the model-view framework. It only takes normal, selected and disabled modes of the icon into account. However, here's one way to work the limitation around:
Qt Code: 
  1. #include <QtGui>
  2.  
  3. class ItemDelegate : public QStyledItemDelegate
  4. {
  5. public:
  6.     ItemDelegate(QObject* parent = 0) : QStyledItemDelegate(parent)
  7.     {
  8.     }
  9.  
  10.     void paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const
  11.     {
  12.         Q_ASSERT(index.isValid());
  13.  
  14.         QStyleOptionViewItemV4 opt = option;
  15.         initStyleOption(&opt, index);
  16.  
  17.         if (opt.state & QStyle::State_MouseOver)
  18.             opt.icon = opt.icon.pixmap(opt.decorationSize, QIcon::Active); // <--
  19.  
  20.         QApplication::style()->drawControl(QStyle::CE_ItemViewItem, &opt, painter, 0);
  21.     }
  22. };
  23.  
  24. int main(int argc, char* argv[])
  25. {
  26.     QApplication app(argc, argv);
  28.     list.setItemDelegate(new ItemDelegate(&list)); // <--
  29.     list.viewport()->setAttribute(Qt::WA_Hover); // <--
  30.  
  31.     QIcon icon;
  32.     icon.addPixmap(QPixmap(":/trolltech/styles/commonstyle/images/standardbutton-no-16.png"), QIcon::Normal); // <--
  33.     icon.addPixmap(QPixmap(":/trolltech/styles/commonstyle/images/standardbutton-yes-16.png"), QIcon::Active); // <--
  34.  
  35.     for (int i = 0; i < 10; ++i)
  36.     {
  38.         item->setText(QString("item %1").arg(i));
  39.         item->setIcon(icon); // <--
  40.         list.addItem(item);
  41.     }
  42.     list.show();
  43.     return app.exec();
  44. }
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