See commons:User:Davepape/Images by others#King Albert's Book for those already uploaded

Was this registered in the US? All PD-US-1923-abroad at least

Commons

  1. Resurgam, Frank Dicksee, PD-old-70
  2. Louvain Cathedral, W. L. Bruckman (Willem Leendert Bruckman d. 1928, PD-old-70
  3. Aid for the Fallen, Thomas Brock, PD-old-70
  4. Charleroi, Joseph Pennell, PD-old-70
  5. A Study, Harrison Fisher, PD-old-70

Here

  1. Queen Mary, John Lavery, PD-old-70 in 2012
  2. Unconquerable, Arthur Rackham, PD-old-70 in 2020
  3. Untitled, Edmund Dulac, PD-old-70 in 2024
  4. The Gloomy Thick Wood, Kay Nielsen, PD-old-70 in 2028
  5. Dies Irae, Maxfield Parrish, PD-old-70 in 2037
  6. Sympathy, James Montgomery Flagg, PD-old-70 in 2031
  7. La Belgique: 1914, Bernard Partridge, PD-old-70 in 2016
  8. The Death of Admiral Blake, A. D. McCormick Arthur David McCormick) d. 1943, PD-old-70 in 2014
  9. Sketch, Leonard Raven-Hill, PD-old-70 in 2013
  10. The Belgian of Tomorrow, William Nicholson, PD-old-70 in 2020

Maybe Commons, if not here

  1. On the Field of Honour, Howard Chandler Christy, check publication history