Author photos into author.php

Howdy,

I’m trying to put a picture to be shown into author.php when the author’s information is queried.

For this, i would upload the picture into the image gallery with the author’s nickname as the title.
in author.php,
if it exists, show it.
if not, don’t.

What would be the code for this?
Thank you VERY much.

Edit 1:
The code would have to make the alphanumeric trimming in order to work to the nicknames.
i.e. “Susana F.” -> “susana-f”