You're going for kind of a polygonal style, so the only real advice I can give you is to try adding some extra grass textures to the hills and ground. Helps to keep everything looking unique and alive no matter what you're making. :)
Some good games to learn from would be the Uncharted games, they have TONS of lush forests but they all look unique without seeming like all the textures were put in at once.
Granted you're not a 200+ people team, but you can definitely learn a trick or two from giving the levels a glance.
Good luck man!