Lovely tiles, especially the last two. Wonderful style - I usually dislike 'dungeon' tiles but these ones are special.

big old trees and less undergrowth
Option 2 looks great, but looks like a tree-stump. 1, 3 and 4 don't look good.
I advise you don't try to be too realistic here - just use your normal smaller trees and don't try to create a realistic big old tree with high foliage - I've seen lots of people attempt to show this on maps and it always look crap.