The changed with the trees has to be something to do with the reduction of the hi-res image to lo-res. The only thing I changed was that I changed the color from black to the brown you see. I also removed the drop shadow. I am not sure how that would increase the thickness of the trees.

As for the hills, I thought along a similar line that I should have some "hilly" regions but I just haven't gotten around to "dressing up" the rest of the terrain. I was considering making brushes for plains, swamps and such and seeing what comes of it but I am not so sure I want to clutter up the map.

The darker and more varied hills, I will have to address that and see what happens. They do seem to have lightened considerably with the transition from hi to lo res.