I think a different crop, getting rid of the grass on the right (to emphasize some more negative space for the tree), of course getting rid of the sensor dust, and maybe fixing the light/white balance could've really done more for this otherwise lovely image.
Hi! Nice tones, but the tilted horizon doesn't really seem to suit/help your subject any. Also, you've got some yucky sensor dust (causing blurry dark spots in sky) to get rid of! You can blow sensor dust out of your camera with a special camera air blower...