Akin to what's in campfire, allowing customization of the UI to match the theme of your campaign.
I really love how campfire does it:
  1. The user selects a palate of 5 colors used throughout the UI for backgrounds and the like.
  2. The user then selects 5 more colors for text/icons that has to be shown on those backgrounds/buttons.
  3. They then can select the font
  4. Finally they can select a background image.