Za Canon iMage Gateway:

My Camera > Themes
Here you can download a complete Theme consisting of Start-up Image, Start-up Sound, Shutter Sound, Operation Sound and Selftimer Sound to personalise your camera.

First, preview any one of the themes by clicking 'Try it'. Try as many themes as you like. Once you have made your choice click 'Download' next to the theme you wish to add to your camera.

After your chosen Theme has been downloaded into your computer, you can then personalize your camera through ZoomBrowser EX / ImageBrowser. For further details, please read the Software Starter Guide accompanying ZoomBrowser EX / ImageBrowser.
Any questions?