Unity's Copyright???

Are the Unity Assets like the Big Tree consider trademarked. Because all my characters and buildings are my own design just not the environment(Main Reason I don’t want to get sued)

http://unity3d.com/unity/faq

Can we use the code/art/assets in Unity Technologies’ example projects?

Yes, all assets in our tutorial and example projects may be used in both commercial and non-commercial use in Unity-based projects. The assets themselves may not be resold, however.

I would assume that would count for the standard assets as well, since they are downloadable from the Asset Store, and thus you could “buy” them for free.