A 3d rotating Earth.
I recommend using a black background.
See http://userlogos.webs.com/earth_ani_large_fast.gif
NOTE: The file is too large. Please use this link: http://upload.wikimedia.org/wikipedia/commons/2/2c/Rotating_earth_(large).gif.

Original (2048x1626)- here.
1920x1600- here.
1600x1270- here.
1280x1016- here.
I did not make this.

Here's a theme I made from this.

Fuller resolution can be found here.

Resolution 1280x960

Earth Space Theme

source: http://zygat3r.deviantart.com/art/Dark-Wood-58266349

This was released under the "Attribution-Noncommercial-No Derivative Works 3.0 Unported" Creative Commons license by Danger83, on Deviantart.
I did not make this.

NOTE:
The file was originally 1.39MB, so I had to save it as a JPEG.

The original file can be found here.