trees in the wind. waves of water. grass moving at wind. perhaps a few leaves in the air. rainy and sunny and cloudy weathers and also seasonal effects. like winter. then spring. flowers blooming. and summer follows. hot and sunny. autumn comes after. dead trees and red leaves. also flowers blooming! and a strong water rush 
That would all be cool, but unnecessary. Maybe lightning when there is a nighttime rainshower, but very little else is really all that necessary. However, I have played a game called Armies of Exigo, and while the game isn't that amazing, the tilesets are awesome. They have lots of special effects, and shadows and lighting that makes you wonder what creatures lurk behind the trees. That would be great to have in glest.
And don't go overboard on the graphics. Not all of us have parents who buy us high end computers.
Then buy your own, 
Yeah, cuz all teens have 800 dollars sitting in their pockets, waiting to be spent...
Have you ever had to earn your own money? Earning enough money to buy a high-end computer or upgrade my own would take months, close to a year.
I'm serious when I want some graphical economy. All I am saying is that you should limit your stuff to 3 frames, each. I truly think the spacing between trees should be more, and each tree should be taller and more complex. All the trees look identical and featureless in forest, and winter forest is that with snow on top. If people used 3 trees where they would normally use 9, and filled in the area with impassable space, the game would run just as fast (even if you want many-framed, high poly models).
