ya, I know what that feels. well... thats the problem, when you put that pixels on a background.
and more if all the game is running, those sprites moving on the screen. just dizzing. 
These trees where actually made for a game I am working on, so with the background and everything going on around them, I think these colors work quite nicely, though on a stand alone image, I can see where your suggestion makes sense.
Glad my intriguing title really made you want to click 
haha, and thanks!
I like to draw trees. 
this ones are amazing!. but maybe if you put that green shade more darky, it'll look better. the same with the most dark shade you have there. it should look better with a blue low contrast ton.
Best title ever ! 8D
I kinda like the little leaf effect.
Very cool and a different style