Honestly I don't like the futuristic building on top, but I'm always picky on these elements in TG-work.
I like are the grasses and flowers. The voronoi look cool too, but could maybe use some variation.
The tree looks good and I certainly would keep it. I was thinking about the textures because they look a little low res.
Don't know if you already know this site, but at
http://www.cgtextures.com/ you can find many high-res textures of bark and leaves.
I also have used them on one of my models and it greatly improved the appearance of the tree.
If you need any help adjusting the textures and applying them to your model correctly then just contact me.
Martin