Alas, it turns out that it's actually a picture of a Karaite Chacham, which is still interesting. Apparently this is the Karaite scholar and Chazan Shalom Zachariasiewicz, also known as Shalom Ha-Chelitzi, showing Rohrer the Karaite cemetery in Halicz. Rohrer wrote of him that he was 37 years old, although he appeared as if he was 57, with a bent back. He also noted that his boots were very clean, unlike the boots of "our dirty Jews."
From Bemerkungen auf einer Reise von der türkischen Gränze über die Bukowina durch Ost- und Westgalizien, Schlesien und Mähren nach Wien (Pichler, 1804).
For more see The Karaites of Galicia: an ethnoreligious minority among the Ashkenazim by Mikhail Kizilov.