It's been on the agenda for quite a while now, but the Ubuntu artwork team and Canonical have finally finished work on the new default theme that will be used in forthcoming releases of Ubuntu Linux, including the release of Ubuntu 10.04 LTS "Lucid Lynx" that will be available next month. It's not only a new theme that has arrived, but their brand with other visual assets have also been revised as well.
Accompanying the new GTK theme is a new boot-splash screen for Plymouth, a new Canonical web-site, and a very different Ubuntu logo. Details behind this radically new brand revision for giving Ubuntu a new appearance can be read about on the Ubuntu Wiki
along with screenshots of the new theme and showing off the new logos.