This is how I make my avatars:
I pick my favorite Mika picture.
I open it in the program 'paint' and do whatever I want with it.. like I write my user name.. maybe add hearts.. anything! Then I save it and upload it into my photobucket. From there I go to back onto the MFC site. click on home then click the picture of my current avatar. I scroll down to 'Custom Avatar', choose oprion 1 "
Option 1 - Enter the URL to the Image on Another Website" and put the photobucket link right there!
You would probably be able to upload the pic from your computer (option 2) but my computer wont let me do that for some reason!
Heres a link to an avatar I'm not using! It's up for grabs =]
http://i18.photobucket.com/albums/b101/Fuzzy52kiwi/icon-Mikasing.jpg