Found one of my white whales in the August 27, 1905 Detroit Free Press. Lew Post appeared in three games for the 1902 Detroit Tigers. He is pictured in a team photo for the Mt. Clemens Michigan club.
By my count that leaves 9 20th century major league players with missing photos:
Jacob Livingston 1901 New York Giants - He is listed as Jacob Livingston(e) on bb-ref, but it is almost certainly Harvey Livingston, a minor league pitcher from NYC, I have a photo of him, but without the smoking gun, his case remains in limbo.
?? Harrison 1901 Washington Senators - There is a strong case to be made that this very is J. Henry "Beef" Harrison, who later ran for governor of New Jersey, I have a photo of him as well, but again no smoking gun to close the case. Contemporary clues mention he was from Southern League or from Maryland.
Shorty Gallagher 1901 Cleveland Blues - Maybe my most sought after guy, played for a dozen or so minor league clubs, but was never in one place for very long...often called Chubby Gallagher.
Jacob Fox 1902 Philadelphia Phillies - Scranton boy who lived his whole life there, was involved with semi-pro baseball and football in his home time.
Ed Watkins 1902 Philadelphia Phillies - Military man - played for Fort Williams military base, possibly findable through military records?
Joe Hughes 1902 Chicago Orphans - Definitely Joseph Thompson Hughes, played for Geneva College and lived fairly long and had kids, so should be findable somehow.
?? Hillebrand 1902 Chicago Orphans - This is definitively not Art Hillebrand or Homer Hillebrand as both men were played in South Dakota at the time of the game. One theory is that it is Archie Galbraith, who was a top college player, and possibly a pal of Frank Selee, but it remains unproven. Only clues seem to be that Hillebrand was an alias. He appeared in the same series as Hughes in Pittsburgh and multiple notes mention that Hughes was related to Orphans' player Bobby Lowe, so perhaps Hillebrand's appearance was also was a product of nepotism.
Jack Smith 1912 Detroit Tigers - Ty Cobb strike game. I am not 100% certain that we have the right guy for this candidate either. He is listed as Smith in all contemporary boxscores and then some forty years later is listed as Jack Coffey, so am not sure why the name change. Main theory is he was young/possibly underage and using an alias.
Sam White 1919 Boston Braves - Born in England, but grew up Rossiter, Pennsylvania, was a coal miner. Only played one full season of pro-ball in 1920 with Durham, NC, otherwise had a habit of signing with clubs and either getting released prior to season or quitting. Another of my most sought after guys.
I should also add that there are three 20th century players who are possibly misidentified (and not on tnfoto's awesome spreadsheet) and will need those cases solved and photos found too.
Delos Brown 1912 Chicago White Sox - John Thorn
breaks down the confusing case of Delos Brown, who was signed by the White Sox, but may not have appeared for the club. His appearance possibly belongs to John Albert Brown, a local amateur who showed up at the park for a tryout and in a case of mistaken identity was put into a game.
Joseph "Hap" Ward 1912 Detroit Tigers - Cobb strike game player, the person currently credited had a really weird obit that claimed he played for the Athletics under the name Mike Murphy, but was kicked out of baseball since he was underage...but nothing confirms him to have played in the Ty Cobb strike game.
Ralph Edwards 1915 Philadelphia Athletics - Ralph Edwards was a minor leaguer, while all the notes about the Edwards who appeared for the A's, described him as a Chicago local from the City League or one of the local colleges. I found a man named Liston Edwards who might be the guy, but case is still in progress.