just create a QMenu in the contextMenuEvent(QGraphicsSceneContextMenuEvent *event) function and add QAction in the menu. And u can connect these QAction to different slots which is called when u select a particular option from the menu.
Example:
contextMenuEvent(QGraphicsSceneContextMenuEvent *event)
{
QAction action1(QIcon("./abcd.png"), "action 1", this);
QAction action2(QIcon("./abcd2.png"), "action 2", this);
connect(&action1, SIGNAL(triggered()), this, SLOT(xyz()));
connect(&action2, SIGNAL(triggered()), this, SLOT(xyz2()));
QMenu myMenu;
myMenu.addAction(&action1);
myMenu.addAction(&action1);
}

I hope this may help you.