I really wish you would have given more for me and others to go on here but I like your work and the idea for this so far so here goes.

Finding a direction (idea & composition that you like) should really have been worked out in a set of thumbnails or sketches before you embarked on rendering anything; particularly because getting a pixel-level finish over a large area is pretty laborious and you really don't want to expend that effort on something you're not fond of or that you'll have to redraw later.

If it doesn't look good in a thumbnail it probably still won't even after you've potentially sunk hours into the rendering process.

If you'll allow me to reach a bit beyond the remit of specific critique; from what I've seen of your other work composition always feels like an afterthought. A lot of people, myself included are reluctant to embrace composition sometimes but it really amounts only to doing on a macro scale what you've already doing well on a micro one; namely creating pleasing shapes, leading the eye and finding a sense of balance.  

In my quick 'n dirty paint-over I've just shunted the tree over into a lazy rule-of-thirds type deal but you could really find something more interesting here. You've defined a strong light source then seemingly ignored it; crepuscular light generally leaves long, warm shadows and the tree & back of the hillock should cast a bunch of shadows; this also helps to ground it, integrating it into the scene. Colours I've barely touched but you had one long fairly monochromatic ramp; perhaps you were intending to sort this out later but I would block in from the beginning.

If any of the above sounds a bit overbearing I apologise, know that I do like your work and that this is intentioned as constructive.    



Edit: Grammar, spelling. Also noticed weekly challenge had ended, sorry. Hope you got something out of this anyway.