If you're looking to build your own style plugins for Drupal's Panels module, the following post will step you through how to do so. The functions and files you'll need to declare are a bit arcane and this beats stepping through the panels code yourself. I've found the rounded corners plugin that ships with panels is a good reference to review when you're stuck.
Creating panels styles can be very powerful. You can define certain styles for your client to choose from, so they can choose what type of display the panel pane will be like. This way you keep the workflow clean, your code under revision control, your themer gets to keep his sanity, and your concious stays clear.