A recent Ubuntu 10.04 (Lucid) update just brought the new wallpaper which you've seen in the screenshots posted last night:
If you using Ubuntu Lucid, the wallpaper will come with the updates (so all you have to do is "sudo apt-get upgrade"). If not, download the new wallpaper from HERE.
In case you were wondering what's up with "warty" in the name, that's because after they've released Ubuntu Warty they realized they couldn't change the default wallpaper unless keeping the same name so the default wallpaper had this name in all the releases so far.
In case you were wondering what's up with "warty" in the name, that's because after they've released Ubuntu Warty they realized they couldn't change the default wallpaper unless keeping the same name so the default wallpaper had this name in all the releases so far.