User Avatars, Getting Members to Add One!

I have a lot users who don't care at all about updating their avatar pictures and this often leads to bland looking threads with default avatar pics. I'm curious, how do some of you combat this issue and what do you do to encourage members to upload an avatar?
Create a notice and set the criteria for "user doesn't have an avatar". It certainly isn't magic but helps ;)
Creating a notice certainly worked for me. After that I sent a private PM and it worked most of the time. I ended up with about a 90% custom avatar rating. A custom avatar made the site look so much pleasing to the eye than a default avatar. The other 10% I uploaded a avatar to their account which I felt represented them the best. If they didn't like it, they could always upload hire own.