Depending on what you're trying to achieve, a more dynamic camera angle might help - a view more from one side. Also, to get the feeling as if you're in a cemetary, you could move into the scene a little and play with the cameras perspective so that you get some grave stones larger in the foreground of your scene. Some kind of grass texture on the ground and even some grass objects (some good freebie ones in freestuff from RDNA - if you have P7 I think they're in the RDNA props content library).
Shadows - where there's light there's always some kind of shadows. If your scene is a moonlit night then there'd be some kind of shadows cast from the moon. Or maybe from that light on the cemetary wall if it was lit. Shadows add a huge sense of depth to any scene - there's a whole lot of experimentation you could do there.

Hope this helps some. Keep going - love the trees BTW.

 

PoserPro2014(Sr4), Win7 x64, display units set to inches.

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