I agree with Diamond about the colour, but it's the texture underneath the trees which I think makes the difference. I'd still urge you to consider a more varied density of trees for other forests you add to this map, although I'll also say I like the scattered spacing around the edge of the forest, too.
What problem are you having trying to overlap the trees? Why did you say you were still figuring it out?
(PS: The standing stones look good btw, as with all the other brushes)