Now that Microsoft has opened the Windows Personalization Gallery for submission of creatives, you can expect to see more and more fine wallpapers and themes being released. The Green World theme for Windows 7 is one such example.
Green grass, green leaves, and water droplets hanging from the strands of a spider web against a field of ambient green: Download this free Windows 7 theme and immerse yourself in the cool, calm color of life and health.
You can download this theme from Microsoft.
These themepacks can be used only on Windows 7 Ultimate, Home Premium, Professional, Enterprise editions, but you could extract the wallpapers if you like them and use them on your desktop.