Anchor Schmidt @ Ubuntuforums created a pack with all the official Ubuntu wallpapers and the Fedora wallpapers from Fedora Core 5 onwards. The wallpaper pack only includes the wallpapers which were default in each Ubuntu / Fedora version, and not the extra wallpapers. The wallpapers are available both for widescreen and 4:3 formats.
There is a video with all these wallpapers, which you can watch below:
I didn't make the video so if you don't like the slideshow transitions, don't blame it on me =)