Whilst researching a pastel portrait of Wallace by the Russian artist Mikhail Dmitrievich Ezuchevsky (1879-1928) I found a photograph of him working on a gigantic painting showing many famous scientists, including Darwin and Wallace [click HERE to see the page on which I found the image].
Ezuchevsky working on the 'mystery' painting
Ezuchevsky worked at the State Darwin Museum in Russia for the last 10 years of his life and did a number of portraits of famous scientists (see his pastel drawing of Wallace on THIS PAGE). I cannot find any more information about the 'giant' painting shown above, so if you know something then please contact me - George Beccaloni blaberus1@ntlworld.com