Here's a picture of some of the participants, courtesy of francefidele.fr:

So far, we have:
From +W left,
1 - Fr. Chazal (French, of course),
2 - one priest behind Fr. C.
3 - one in the front row,
4 - one in the back with the candlestick,
5 - Dom Tomas Aquino in front,
6 -
a Benedictine just behind him, Fr. Bruno, OSB
7 - one apparently French priest in the back
8 - Fr. Pfeiffer
9 - and another French priest in front;
Then from +W to the right:
1 - one Dominican (has a hood?) in the middle,
2 - one tall priest in the back,
3 - Fr. Pierre Marie, O.P. in front,
4 - Fr. Marie-Dominique, O.P. smiling, just to the right of Fr. Pierre-Marie, O.P.
5 - one French priest in the front with prayer-folded hands
6 - Fr. Hewko in the back with the candlestick,
7 - one taller priest in front with hands folded over his missal
8 - one priest in the back,
9 - and finally, the younger-looking one on the far right.
If anyone can fill in the names that would be great! You can use these numbers, just say Left#3, or Right#7.