hmmmm, how about adding some thread painting to the trunk and leaves. I like the suggestion about using more leaves, even if they don't have names on them, they will fill out the tree. (you could always add a name here and then in the future if you wanted to)
A wonderful project! And walking away for awhile will help you with figuring out how to make it more pleasing to yourself.
I'm sure you'll get some great ideas from the gals here.