Well, I have to disagree with Richard. In my humble opinion and definitely to my personal taste I like daylight much better.
If you get the moonlight to work then that would be absolutely fantastic, but I have barely seen a photorealistic, let alone realistic render with moonlight.
It's an extremely tough nut to crack, so I would give it some thought before putting much precious time and effort into getting this type of lighting to work + meeting the aims of the contest.
So far I must say it doesn't look bad at all when you look at the vegetation.
About the vegetation: perhaps you can decrease the scales of the vegetation by half to give the image more depth and scale.
The road may seem a bit wide then.
You can of course also increase camera height to 'fix' this, but still there would only be X number of trees in between the camera and the distant hill instead of 2*X trees, see?
When I build my scenes I often start my populating my scene with trees to get a fix on my scales and final POV.
The size variation I set to those trees will be the size variations for almost all the other models I load into the scene, given that they use similar scales in metres (for example).