There is much texture details, but imho too little contrast, making the whole character hard to look at. Contrast is a great way to add volume, too. And at some places (esp. the front arm), you could definitely use more detailed volume, with a clearer lightsource.
That could be sketched on a flat-color copy of your picture first, imho, so that you can try several combinations before blending them into the final picture.

Don't hesitate to make those vines-stuff (greens) swirl more to give them a more organic look.

My best advice would be to check a 3/4 cylinder tutorial and build a model of your tree as a stack of cylinders. You can then overlay that model against your art to check you fit to the perspective you want to follow.

I think it would definitely benefit if you drop the dark outlines around the 'layers' of leaves.

Hello. Nice work on the rocks, but it is a bit surprising to see them laser-cut to have 135° shapes at the edge of the mockup.

You brought some improvement to those dark-green pillars, but they still suffer much from having their highlight precisely on the edge. You typically have that only with cubic items or with very specific lightning. Most of the time, highlight might be _near_ the edges, but not precisely _on_ the edge, unless you want to make them look sharp and your object angular, like you did for the (brown) rocks (top of the picture). May I ask you what material you want them to be made of ?

Both rocks, however, would benefit from having highligh-on-sharp-edges only when they're in an area in the light. That especially needs fixing with the purple rocks as the contrast is much higher there.

I think http://3.bp.blogspot.com/_LtwkN4oRTe0/StTqvcWP6oI/AAAAAAAABpY/fXsXEf-ZfDk/s320/ziggyforest.png could be an interesting reference for you.