Hello Linux Geeksters. As you may know, the Ubuntu community is submitting wallpapers every six months, for each Ubuntu release, and the developers choose among those the default wallpapers of the next Ubuntu version.
Recently, the developers have chosen the default wallpapers of Ubuntu 14.10 Utopic Unicorn. And they really look awesome.
To get the Ubuntu Utopic wallpapers and place them with the other wallpapers, on your system, do:
$ cd /usr/share/backgrounds
$ sudo wget "https://bugs.launchpad.net/ubuntu/+source/ubuntu-wallpapers/+bug/1354341/+attachment/4199899/+files/14.10%20images.zip"
$ sudo unzip "14.10 images.zip" && sudo rm "14.10 images.zip"
Because the process of picking the default wallpapers is subjective, you should see yourself all the submitted wallpapers from the contest and download the images which you like. You can see all the images on Flickr.