As andlabs UI is a toolkit that aims to provide an abstraction to standard widgets (and therefore using the current platform's look and feel), customization options are limited. The only facility to introduce custom elements is the ui.Area widget and the draw features we explored. This enables a company font or logo to be drawn (support for loading images is said to be coming in a later version) at a certain location in the interface.
If you are looking for further abilities to customize or theme the applications you are building, then andlabs UI may not be the right solution for your project. It's probably better to explore GTK+ or Qt (which we cover in Chapter 6, Go-GTK - Multiple Platforms with GTK, and Chapter 7, Go-Qt - ...
