You can edit or customise your profile by adding text, images, your own voice, and even links to the other Yahoo services that you use.
Go to the Yahoo Member Directory
and click My Profiles
in the upper-right corner of the page. Click the "Edit" link next to the profile you want to change. You can edit your profile on the next page.
The profiles edit page shows you exactly what other users see, except that the yellow edit bar is not present. You only see the edit bar if you are logged in to your own account and viewing your profiles.
To learn how to create your own sound file to use in your Yahoo profiles, please read How do I add a voice clip?