Those hills in the back look a little too rounded and pillowy, in my opinion. A more gradual, rolling hill might be a better effect.
Also, the blue tube thing for gravel (It's late and I don't remember the name of it), is really low to the ground for it's purpose. Those things are used to dump stuff into the back of dump trucks, not act as a gutter.
You have a great oppurtunity to play with lighting a bit, might want to look into a bit more!
my 2cents.
Beyond all that, love the theme you've put together, the green accents in some places are really nice.