We use the common sense approach :)
If you post photos all day of your face, then it's clear if you take a photo of yourself with a timestamped paper that you're the same person who owns the account.
As per our recovery page, it doesn't even have to be a photo of yourself, we've done recovery requests in the past where people have verified their accounts using their pets, or unique objects around their house.
A verification photo showing your account name, "anonsteem", and the current date on a piece of paper. The photo must be of something clearly visible on your account blog - send us the link to the post showing the previous photo/video, this could be a photo of yourself, a pet, or of a unique object in your house which you have shown on your blog.