The sky is beautiful, but it works best as a backdrop for landscapes or if it has something in it like clouds, plane, stars, whatever. Shooting tree tops is a good idea too, but maybe more of them would create greater interest and more use of the space. You are on the right track. Keep posting. I'd like to see more from you.

I love what you have tried to do here by picking out the detail in the branches against the sky however, i do think that there is a little too much sky and not enough subject matter. Have you tried cropping some of the sky out to make it a little more balanced? Hope this helps :)