After receiving feedback from fellow classmate, Carol, I went back and made changes to my originals, incorporating her suggestions. This is the first revised "tree":

And this is the second tree:

I decided to go back and see what I might do with the yellow/black colors as well as create a leaf in PI. Once I did something - got out of paint mode? - I found I couldn't go back and make adjustments to the layers. So this is what I've got now - and I'm sure there's a way to be able to paint on those layers again.