Biographical information on him is almost non-existent on the Internet. Very brief items are here and here. A web site devoted to him is here. It is in French and contains a little more information, but mostly mentions aspects of Provençal nationalism.
Denis-Valvérane's paintings found on the Web tend to be somewhat mediocre in my opinion, but some of his cartoon work strikes me as being very good. Examples of each are shown below.
A scene from Denis-Valvérane's home town.
The man's shirt and hands are done well.