Add Overlay to Avatar for Twitter Users
Twitter users can make their avatars look cooler by adding overlays. This is where Avartize plays its primary role. Avatize is a free service anyone can use easily to add overlays to avatar. Beside letting you to upload an avatar and then modifying it according to your liking, Avartize also allows you to use your twitter credential to login and add any available overlay to your avatar. This overlay can be turned off anytime you like.
If you want alternative online services to customize your avatar, then you can try mypictr that allows you to create avatar online, or faceyourmanga to create manga avatar, or avatar photo that lets you create animated avatar with plenty of animation effects available for free.