Wow, I'm loving the lighting on the foreground, especially the girl's face! The fireflies are also a nice detail which give the scene an even more "natural" feel, particularly because you paid attention to depth and made all the bugs vary in size. I'd normally like a more detailed foreground (the trees in front), but the style works well here and I personally have no complaints about your decision to go for silhouettes.
On the topic of lighting, I think the sky needs a bit more work to look great: for once, it looks empty compared to the rest of the scene, so adding a few thin, wispy clouds may correct that. However, you can argue that the sky isn't always cloudy, which is true ^^". In this case, try making it a bit darker, since it's supposed to be an almost-night scene. Secondly, it looks like there's a giant spotlight behind the mountain on the right and an additional source of light on the left. Since this scene takes place somewhere in nature, arguably far away from a city, the sky should be a lot darker and the only light should come from the moon - which, judging by how strong the light here is, should be a full moon - and (less) the stars.
There are also a few JPEG artifacts and stretch marks on the mountains on the right, but that can be fixed by saving with higher quality settings.
Overall this is a pretty good work and makes for a good desktop; it's spacious without being empty, colorful without hurting the eyes and calming without being boring. You've got a good sense of lighting and I look forward to seeing more walls from you :) Good job!