If you go to your profile, you can upload a avatar. Just click on the circle with the + inside it towards the top, lefthand side of your profile.
If you are trying to upload a large photo then it might fail. Try it a few times or manually reduce the size of the photo before trying to upload it.
Or you can mail the image that you want to use to firstname.lastname@example.org and I will upload it for you. Be sure and include your handle so I know which profile to attach it to.