In the web http://cesium.duniter.fr you can edit your profile and upload a photo.
Is this photo saved in the Blockchain?
I’m curious about that.
No, data like “user profile” (+ market place, professionals registry, private messages) are stored in a P2P cluster, that used an embedded ElasticSearch (=ES) cluster (see Duniter4j project).
Basically, all stored data are signed using crypto keys (same as Duniter).
Some private data, like user settings and private messages are also encrypted using NaCL authenticated encryption.
To understand how ES + Duniter4j works, you can follow this tutorial (in French sorry) or read this presentation (french).
Some Cesium’s features (like market place and professionals registry) will go in a new project (outside Duniter) called ĞChange.
Additional features, such as real time notification (“you received a payment”, “a certification”, …), will be added soon. This new data will be generated by ES/Duniter4j nodes, when new block are detected.
Hope this helps 
Your avatar could be see here : http://data.duniter.fr/user/profile/4qesC5stf342FJL7w5AQndwc3GmrxA49DdUZcZt4Ti2c/_image/avatar.png
Each user can send to ES node a delete request (signed by its crypto key) to remove a data that he owns.
OK. Thank you!
you can follow this tutorial1 (in French sorry)
Don’t worry, I understand French, can’t write it, but I understand.