how about filling it with some design theory?
a good composition is filled, but not with
clutter. there needs to be a contrast of open to dense. I say move your good stump up to where the more wippish one is, and get rid of the little WIP bush...also those clouds under the castel destroy more depth than they suggest because the colors cut into the form rather than sitting in front.
Also, the guy is supposedly the focus of the piece, but he's pushed all the way over to the side? and the donkey, for all it's complaining, doesn't look to be struggling at all under the weight.
these are the important things, not stumps in the foreground!!
I know demoscene has rarely been about effective communication or composition, but honestly the worst thing you could do for this piece right now is throw a bunch of junk in.
(as far as the speech bubble goes my vote is for a caption)