Arms of Lieutenant General Vincent Marie Duviver (1774–1851).
Arms of Vincent's younger brother Lieutenant General Ignace Louis Duvivier (1777–1853).
I don't know much about the said persons, but there is a Wikipedia article about Ignace Duvivier in French and Dutch. The article includes a photo of a memorial which I believe I saw during my visit to Mons (Bergen) in June 2000. A photo of the Duvivier arms can be viewed here.
Not sure what I am going to do with the litographies, but they are quite nice. Maybe I should frame them and put them on the wall?