Microsoft has released 2 more themepacks for Windows 7 at its Personalization Gallery: One for Space lovers called the NASA SpaceScapes and the other for Wolf lovers.
The NASA SpaceScapes themepack & the Wolf themepack has 14 & 11 cool desktop wallpapers, respectively. Roam the far corners of the universe—distant galaxies, dying stars, and the echoes of the Big Bang—with this NASA theme for Windows 7.
Windows 7 uses the .themepack file extension for its themes, whereas Windows 8 uses a new file extension .deskthemepack. While you can apply Windows 7 themes on Windows 8, Windows 8 cannot be applied on Windows 7.
Windows 7 themes can only be used in Windows 7 Home Premium, Professional, Enterprise, or Ultimate editions, but you could extract the wallpapers if you like them and use them on your desktop. If you have a wonderful collection of wallpapers, you can always create your own Windows 7 themes too!