the same picture can be seen on Gilliard book page 225 "le destin tragique de Nicolas II et de sa famille" (Payot - 1921). So we can think this photos has been taken by Romanov relatives during time between Romanov arrival and time relatives were banned from Iekaterinburg.
A the beginning of the book, Gilliard aknowledge "L'illustration" which provided all drawings and photos. Then, maybe photos are from "L'illustration"... You should consult Elysée Muséum in Lausann where Gilliard has put all his remembering to know more about this
Regards