One of the 20th Anniversary wallpapers shows the evolution of the Ubuntu logo, which has had three renditions to date. Another is the brown Warty Warthog default wallpaper, but the old Ubuntu logo ...

Ubuntu's logo retains its essential shape ... 15.04 may have had the codename "Vivid Vervet," but you wouldn't know it from the wallpaper, which had been an abstract blend of purple and orange ...