Northern Europe

Rav Deutsch emigrated to the United States in 1891 and got himself in trouble for his politics during WWI.  Like his contemporaries from late 19th century Austria, he also did not wear a kippah.

Considered an Orthodox rabbi, he nevertheless did not wear a kippah.

An Orthodox rabbi, Rav Lehmann fought against the growing Reform movement.  He continued to wear a black velvet kippah even when some of his contemporaries did not.

Rav Kayserling followed the late 19th Century practice of not wearing a head covering at all.

Another tricorn hat.  I hate to say it, but I think this is what Dutch Jews wore.

Rav Hirsch had "considerable" influence on modern Orthodox Judaism.  And he wore a small black velvet kippah.

Another small black velvet kippah, so typical of the mid-19th century.  I think I'm starting to see the answer to my original question.

The only rabbi with a portrait from Amsterdam.  Goodness, I hoep this isn't what Dutch Jews wore.  Frankly, his hat doesn't look Jewish at all, although I'm not sure the Russian fur caps or turbans do either.

Shown here wearing a small black velvet kippah, he was also painted wearing a large Russian fur hat.  This makes me wonder whether there wasn't a greater variation among all rabbis in the 19th century.  My data is too limited.

This hat seems much more similar to the smaller black velvet kippot that would sweep Europe later on.