Hi Stuart, there're two approaches for custom buttons:
1. Use our API (programming interface) and control the viewer using your own buttons.
2. Customize selected skin by changing skin's CSS (e.g basic.css) and/or the button images it references. The images are usually located under imagerotator/html/img/your-skin-folder and the CSS files are under imagerotator/html/css.
Let us know if any questions!