For Maverick, we simply refined the artwork we implemented in Lucid. Natty might have some more aggressive changes and further refinements.
New Colour Pallette
The colour pallette has been updated to reflect the actual colours used in Edubuntu 10.10. The dark grey colour has been updated to #424242 to match the Hitch Hikers Guide to the Galaxy theme around the 10.10 release. Our new official green is also a bit lighter and brighter, it turned out useful in the installer slideshow to make it somewhat more cheerful.
New Ubiquity Slideshow
Above is an example slide, visit http://people.ubuntu.com/~jonathan/files/maverick/ubiquity-slideshow/ to view the entire slideshow.
Default menu icon now applies to the gartoon theme too. Currently it's applied per icon theme with diverts, which is certainly not optimal. We'll look into improving this and liaise with upstream to improve this.
During the Maverick cycle we have updated both the content of the Edubuntu website as well as its theming to reflect the current Edubuntu branding.
For the first time ever, Edubuntu has a countdown to release banner. It needs some refinement and we haven't made much splash for it, but we'll work on this for the next release.