First of all, trees doesn't grow that wide apart, thew grow in "packs" (lol, brainfreeze on better words). Also, i think the trees are to small and unvaried, try downloading the
Ultimate Terraining Map, and pick some nice trees there.
Also, there is nothing really happening in this scene. That is what i meant by focal point. That crypt is simply not interresting enough, you should try to make buildings by doodads. Also keep in mind that vegetation grows in shaded areas, like beneath trees, and MOST OF ALL: why are there leaves on the ground, when there are no trees above them? Where on earth did all those leaves come from?
Here are some nice shots of similar terrains with nice focal points:
Picture 1
Some ruins in a cave, done by Keji. Notice how the glowing altar in the center immediately catches your attention.
Picture 2
Taken from Naze's terrain gallery. The hill makes a nice contrast in the view, and is a logical place to build a structure on. In your terrain, the ruins seem more like shoved into a corner, which is not too appealing.
Picture 3
Having objects at the sides like this makes a natural frame for your terrain. This does not have to be trees, you could make it cliffs, towers, or whatever, the effect is still the same.
Notice that all those terrains use fog. Go to the scenario options and make yourself one too.