What I mean by that is that the vegetation is way denser than it is acceptable in a framed scene. It is nice, tranquil and lively but it is too crowded. Which makes it seem forced when first looked at.
I'd either trim the forest (no pun intended :b) and variate with vines, webs and some insects around or zoom in further.
The rocks, on the other hand contrast too much with the hq textures and would benefit if either being squeezed and playing with the felsen models or Talavaj's Cove rock models. Also, some fern and bush models with hq textures could be added around the trees once the forest has been trimmed a tad.
The statues could be integrated into some form of shrine or altar. Details are definitely needed in that corned to add further variation to the composition.
Now, for the water, what you seem to lack is depth, details, believable reflections and some various color tones.
First, try playing with some water plane models at varying scales and position plus tinting and then try to add some minute waves at different points. Afterwards, play around with either the cloud models or the nebula one to achieve some color variation on the surface.
Variation, details, depth, color and life. That's what your lake needs.
As for the sky, It is too bright, intense and lacks some well needed glow models at lower tints. The 'star' models used for the sun are too intense and reek of a fake light source. Try playing around with those more at lesser tinting values and compliment the sky with nebula and glow models.
Search for some sky references if you feel like you're lost your hold in that department.