Trees from 3D Warehouse: http://sketchupland.posterous.com/best-3d-trees-from-3d-warehouse

I agree with Andy. If you load the defaults, you should get a fairly decent rendering using the SU sun.

I second what Solo said. Composing the view beautifully is half of the rendering process. Also look at Arrowway for a brick material that has a bump and specular map.

It looks like that darker color is that crappy tan default material color SU applies to faces. I would make a new material and make sure to re-apply it to all the geometry.