Theme Builder is a third party application BlackBerry 10 owners can use to create custom homescreen icons for various apps and settings on your device. For a limited time, you can download a free copy using the code CBTHEME.
Themes have always played an important part in the BlackBerry experience. They provide a way to customize your device the way you want. In addition to swapping wallpapers, another way you can personalize your BlackBerry 10 handset is by utilizing a third party app for deeper customization. Theme Builder is one such method for changing certain aspects of your home screen, more specifically, the icons. Using this app, you can create custom home screen icons and shortcuts for native, third-party, and system apps.
Source: ANDRIOD CENTRAL