If you're already working on giving your Android device that Jelly Bean clone look and feel, you can start with the official boot animation and wallpapers. All the official files have been nabbed from an OTA update for the GSM Galaxy Nexus that was handed out to I/O attendees.
Luckily the good folks over at @kovdev have packaged the wallpapers up in a convenient .apk for your downloading pleasure. Right now you can grab the pack from DroidLife in the source link below, but @kovdev says they’ll have it up in the Google Play store shortly.
Separately you can download the Galaxy Nexus Jelly Bean boot animation from AndroidAuthority (also linked below). You’ll need to be rooted to use this one. Simply copy the .zip to your device and then with the file manager of your choice, move it to /system/media/bootanimation.zip. Be sure to backup or rename your current bootanimation.zip file in case this one doesn’t exactly tickle your fancy.