I should be given a prize for answering this one.
take any picture, resize it, cut it, do whatever you want with it. save it has a 70x70 gif. Upload it somewhere or use the lucasforums custom avatar feature. Voila' you have your custom avatar! It's all in your edit options in your user cp. Where to get pictures? Well, I won't answer that, I will let you find out so you can evolve to a higher life form.