I did a remix of the Fallen Tree and one of the Tree Stumps from kevinrau's RPG and Wargame Scatter Trees Stumps Rocks set. He has a lot of great stuff so check it out. These are fantastic models, but my printer sometimes needs a little help to print properly.
I played around with the geometry of the models, making the bases a little fatter, smoothed out the bark a bit, added some texture to the stump tops, and plane cut the bases so they would print flat.
The models are fully scaleable.