How does one theme a panel (or add a style)
When you add a CSS class using the "CSS Settings" for the pane, Panels will tag the panel html with the classes you have identified.  You can then specifically change the css styling attributes by defining your class style using the local.css file found in the active theme directory (set in admin/appearance) to modify your targeted content.

IF you are not familiar with working with css , I suggest you get an intro level book on Drupal and theming, a basic primer on css coding, and upload firebug for Firefox browser to help you see which css styles are currently rendering any content you display on the site.  

I have not found a good out-of-the-box solution for what you want to do. I hope this helps get you started on the 'custom route'.