You'll need to purchas a copy of the iLIfe disc from a 3rd party retailer like Amazon.com or eBay.com. iLife 11 comes with only iDVD 5-7 themes and the Software Update doesn't offer the other themes any more.
The only sure fire way to get all themes is to start with the iLife 09 disc:
This shows the iDVD contents in the iLife 09 disc via Pacifist:
You then can upgrade from iDVD 7.0.3 to iDVD 7.1.2 via the updaters at the Apple Downloads webpage.