I was struggling to override the icons on a tree with our style sheet (done pre 11.1.4) nothing I was doing was working (the icons remained) - tried using af|tree::expanded-icon-style, af|tree::expanded-icon etc.
So if anyone is struggling with this here is what I did to fix this - I just created a new style sheet using the nifty new adf style sheet item and found my tree item I wished to override. I then used the new style sheet in my app and everything worked as expected. (I suspect this was do with a spelling error but the new css editor makes this a thing of the past)
The reason for this is I want all the auto tree icons to dissapear and add my own icons to the facet to denote what each tree item is.
css source -
@namespace af "http://xmlns.oracle.com/adf/faces/rich";
@namespace dvt "http://xmlns.oracle.com/dss/adf/faces";