ALV Tree leafs

I'm extending ALV Tree, which dinamicaly build it own structure. I'm trying ti find function/property which can change view of my leaf, precise:

when we have leaf with no subleaf when this leaf is shown with special icon (looking like notepad icon),

when we have leaf with subleafs then it is shown with folder icon.

I want to change some leafs which should be loocing like leafs with folder icon, beacause in future, some data for this leafs will be read and some subleafs will appear (this reading will be performed, when user click on this leaf and will try to expand it).

For any help I reward in points