You could choose either a cartoon or a photo avatar
Cartoon.
The Yahoo avatars page is no longer available but you can do this:
Create a personal avatar below save it to you pc then upload it as below.
http://freeavatarsonline.com/
http://www.avatarsdb.com/
http://www.free-avatars.com/
Photo and avatar upload
Click on your current avatar then click edit my preferences to the right of your default avatar click update photo. Follow the prompts to upload a photo or saved avatar from your pc.