You can download Today themes for the 9700 from PimpMyBerry! - Pimp Your BlackBerry! and other theme web sites. Check out the Media forum here. Also, some 8900 themes work properly on the 9700. I'm using an old "U" theme.
Edit - just found it... there are additional settings for each theme (new compared to my 8830) that allow you to change the background and the style of theme.