Thanks. I really never added it myself. Maybe this site is somehow connected to another where I've previously uploaded it, e.g. Wordpress? I only registered here today and certainly never uploaded a photo. I presuming others can see my photo as well as me?
If I go to Settings > Edit Avatar, this is what I find:
No Avatar Specified
Avatars are small graphics that are displayed under your username whenever you post.
Do not use an avatar Note: if you have a custom avatar selecting this option will delete it.
The 'Do not use an avatar' box is checked