I think #19, #20 still open? I searched through a few Popes looking for #20, but no luck, although some of the Popes made it up on to this list of Evil People.
Can I offer #24? Clue: Common sense. (Dark painting on the right.)
Can I offer #25? Clues: Polish science, studied in France, Nobel prize for Physics in 1903. (Woman in the middle.)
Can I offer #26? Clue: Russian science, one for the chemists. (Clue 2) (Wild man on the left.)
Can I offer #27? Clue: “The book, which went on to be widely copied and imitated, introduced the Hindu-Arabic place-valued decimal system and the use of Arabic numerals into Europe. Indeed, although mainly a book about the use of Arab numerals, which became known as algorism, simultaneous linear equations are also studied in this work. Certainly many of the problems that [that man] considers in Liber abaci were similar to those appearing in Arab sources.” (The charcoal drawing.)