Are you setting the icons on tab using style sheets or code? I assume code as i don't see any code to set icons in the style sheet you posted. Also, i don't see any option to set the tab bar icon using style sheet in Qt documentation, so i am curious.
I am tinkering around with the same thing but i don't see any option to change the icon position unless you subclass QTabBar and do the drawing yourself.
Maybe try playing with the "align" stylesheet property.