Mrs. Kingsley
Portrait: "Mrs. William Playfair", 1887
Miss Helen Kingsley
Portrait: "Mrs. Ralph Curtis", 1898
Arabella Majors
Portrait: "Lady Agnew of Lochnaw", 1892
Thomas Keller
Portrait: "Jean Joseph Marie Carries", 1880
Note that obviously any portraits here should depend on the player's choice, but since I was browsing I thought I would offer some suggestions.
Dr. Alain Westbrook (Gordon)
Portrait: "Arthur Daintrey", 1882
Henry Severn Jr. (Tor), son of wealthy factory owner & senior at Cambridge
Possible Portrait: "Walford Graham Robertson", 1894
Philip Majors (Guin), a painter based on John Singer Sargent
Possible Portrait: "Self Portrait", 1886
Humboldt Kingsley (Liz), aristocratic professor studying native beliefs
Possible Portrait: "Edmund Gosse", 1886
Possible Portrait: "Henry Cabot Lodge", 1890
Thomas Coneybeare (Jim), librarian, philologist, & literary scholar
Possible Portrait: "Claude Monet", 1889
Possible Portrait: "Henry Lee Higginson", 1903
Possible Portrait: "Joseph Joachim", 1904
Lydia Brookmyre (Bill), a socialist teacher and freethinker
Possible Portrait: "Mrs. Henry St. John Smith", 1883
Portraits considered for characters, but not used:
Possible Portrait: "Mrs. Charles E. Inches", 1887
Possible Portrait: "Mademoiselle Suzanne Poirson", 1885
Possible Portrait: "Mrs. John J. Chapman", 1893
Group Portrait: "The Misses Vickers", 1884
Possible Portrait: "Sir Hugh Lane", 1906
Possible Portrait: "Dr. Robert Farquharson of Finzean", 1881