Esperanto photo archive at Harvard Library

Harvard Library Visual Information Access can be searched for 'Esperanto', yielding 6 results. All photos originate from the Central Zionist Archives.

Results #5 & #6 actually consist of two images apiece. # of these are apparently identical photos of L.L. Zamenhof; the last is apparently a photo of his father, Marc Zamenhof. #5 dates the Zamenhof photo at 1908.

#1 is a photo of Zamenhof's grave.

None of the above photos are of good quality. However, there are 3 photos of excellent quality.  They are, respectively, from the 5th (1943), 6th (1944), and 7th (1945) Palestine Esperanto Congress, Jerusalem.

I had no idea that there were Esperanto congresses in Palestine, let alone during the Holocaust of World War II whilst European Jewry was being exterminated.  There's a story here.