You can create your own themes using Plazmic Content Developer's Kit v4.1 for BlackBerry   For it to work you will have to have BlackBerry Java™ Development Environment (JDE) v4.1 or higher installed on your computer, available here . This in turn requires that you have Java 2 SDK, Standard Edition v5.0 on your system (free download from Sun). Once you get all this installed, fire up the Theme Builder and away you go.... Change font, colors, backgrounds, icons, etc. See screen shots below:
Here are some pictures, first of the built-in Insight (icon) theme and my first attempts at something different, my "sibelle" theme & a Swiss cantonal flag theme: