Welcome to the forum.
When PrE 9 was introduced, there was a subscription to Photoshop.com included. In many countries, there was the ability to buy the "Plus" subscription, that allowed greater storage capacity, and also some additional content, including a few new Themes. Fairly recently, Photoshop.com was replaced by Adobe Revel, but I do not believe that it contains any new Themes.
Many Plus members complained, as there was never really much in the way of additional content. Not sure what had been planned, but it never seemed to have materialized.
At this time, I know of no additional Themes.
IIRC, there was a member on Muvipix.com, who was working on creating more Themes, but I am not sure how that project went - if it went, at all. You might want to go to Muvipix.com, and inquire in the PrE forums, just in case those extra Themes WERE created, and are available.
Have you downloaded all the Premiere Elements 9.0/9.0.1 content?
If so, then you probably have as much as is available. There were scattered reports on how to make one's own, but the bottom line (easy way) seems to be, if you want something different than what Adobe has provided, then you take Adobe's Instant Movie and customize it. After the Instant Movie is created, you can right click it on the Timeline and select Break Apart Instant Movie. Then do your editing of the components that went into the Instant Movie.