Panels 2 Theming:

The following issues and posts are some material for Panels 2 theming documentation:

• #218960: Styling "Rounded Corners"
• #217553: New Styles, with Photoshop Templates, ready to be shared and added to the code!

General HowTo background on custom rounded corners themes:

• http://www.alistapart.com/articles/customcorners/
• http://socialsynergyweb.net/cgi-bin/wiki/HomePage

Panels styles:
Several module supply further styles for panels and panes:

• Panels tabs style: group several panes together into tabs.
• Collapsing Panels Style: panes that can be collapsed and expanded.