A few weeks ago P3Droid and TeamBlackhat leaked the official Galaxy Nexus bootanimation. He was even nice enough to pack it into a flashable.zip to make it easy for us! Below are the download links and install instructions.
BootAnimation_Flashable.zip file: Mirror 1, 2
1.Get to ClockWorkRecovery however you do that
2. Then just navigate to "install.zip from sdcard"
3. Navigate to "choose .zip from sdcard"
4. Then find the .zip (Should be in download folder)
5. choose then install, select yes
6. Reboot... viola new bootani!
Bootanimation.zip Mirror 1, 2
Grab Root Explorer from the market
1. In root explorer navigate to System/media press and hold the Bootanimation.zip select rename and rename to bootanimation.bak so you can revert to stock ani if you dont like it(you may have to enable r/w by clicking the button in the top right)
2. Navigate to your sdcard/download find the bootanimation.zip hold and select "move" from the menu
3. navigate back to system/media and select "paste"
4. Reboot phone... viola new bootani!