And also, any original picture of your RHG would do. It just has to be drawn. It could be a picture of your RHG that you drew on paper, or you could go to a local library or somewhere that has printers/scanners and just use that. One of the main reasons why everyone has a problem with your RHG is because of the obvious minecraft references and picture.
To change your avatar, go to settings, look under profile, and click edit avatar. If you look under "custom avatar" you'll see two options. Option one is to lnk to an image or gif that is 185 x 185 pixels. The second option is to choose from one of the files on your computer.