The sticky Oniya provided a link to is mostly pertinent to personal pictures that you wish to share of yourself. Often, you will take pictures with other people - say, friends and family. We do not want you to share images of people who are not able to give you permission to share a picture of them on Elliquiy, a site that they may or may not know the content. Sure, it might be possible to get permission and prove it, but it's easier if we ask you to just blur out their faces so that their privacy is protected. Obviously, your own face would be untouched, as that would be the reason you would be sharing.
On the subject of your avatar, the rule reads that you may not use images of, say, your best friend or your sister. You can use images of yourself; you may also use images of public figures (celebrities, musicians, and actors/actresses are popular choices) as well as semi-public figures, whom I would assume to mean people who aren't necessarily "well known" but who do legitimately have a public presence of some sort (for example, amateur models or actors/actresses come to mind) and put their own images on the internet.
Now, I wasn't sure if you were referring to yourself when you asked about amateur porn images for a character images (I apologize, I had read your question as asking about an avatar). If you are asking about yourself - yes, you can use pictures of yourself as an image because (1) the picture is of you, and (2) you would probably count as a semi-public figure, and (3) you have the distribution rights to your own image. If you are not asking about yourself, and the image is of someone else who is a porn actor/actress, the answer is still yes because of (2) s/he is a semi-public figure.
