I am not sure how to add your own avatar since you have to use a link (I know I am showing my ignorance, now) I have pictures to use, but there is no "link" to add... any suggestion? If not, I will just keep the one I found in the "library"!
Upload your pics to a place like www.imagehost.com so that they have a 'www' address. You will then have a 'link'. (it will give you a URL for that picture). You may have to rezise the photo though, depending on it's size, but most uploaders give you the option to do so when you upload it. I'm not a pro at this either, but maybe that will help.
I use image station or photobucket...you have to down load your pic there, then add the url to the avatar section....right click on the image, then copy the properties link...good luck and let us know if you can't figure it out.