These icons can be replaced by any 16x16 image to your pleasure! :)

fc.gif and fe.gif are the inner "line" and "L", respectively; and 
c.gif and e.gif are the "closed" and "open" folder icons, respectively.


I've created some extras for you ... ok, they were my first versions.  For any number of reasons, I didn't like them but kept them, in case you wanted to play around with the tree images.  The extra folders (alt color, books, default, trans, & white) can be deleted with no harm to the tree.