Numerous painters chronicled aspects of the Vienna Congress, including the great Sir Thomas Lawrence, who made portraits of many of the principal participants—notably Alexander I (only in the post-Congress Congress of 1818), Castlereagh, and Metternich.
On the other hand, the Paris Peace Conference was in some regards more problematic, since the medium of painting was undergoing such upheaval, and since by 1919, the photographer had overtaken the painter as the "natural" visual chronicler of great events.
Still, there was at least one painter who was commissioned by the British government to record the Conference, William Orpen.
Orpen was an Irish painter born in 1878 who had become one of the official painters commissioned by the British to record the war fronts for the British public. As with many other painters, there was trouble with Orpen. He was fine portrait painter with a non-academic, lightly Modernist style, and he did indeed make portraits of Ferdinand Foch, Douglas Haig, Herbert Plumer, and other important figures, military and political. Yet the more he observed the Western Front in person from about the middle of the war onward, the more he began to slip from the themes dictated by the War Propaganda Bureau for which he worked. His Dead Germans in a Trench, for example, didn't really do much to extol the glory of war. Nor did his scene of a young mother taking a break to nurse her child as she works to tidy up the war grave of her husband.
He then received the commission to attend the Paris Peace Conference and paint the principle scenes and personages. Orpen did paint portraits of many principals, but as we have seen, there were not too many great scenes, only two plenary sessions after all. And Orpen painted both of them, plus many other gatherings (as in the January 18 plenary, in the image above). Of the opening meeting, he wrote in his memoir: "For a seat, I was usually perched upon a window sill. It was amusing to sit there and listen to Clemenceau (Le Tigre) putting the fear of death into the delegates of the smaller nations if they talked too long. President Wilson occasionally arose and spoke of love and forgiveness. Lloyd George just went on working, his secretaries constantly rushing up to him whispering and departing, only to return for more whispers."
When Orpen first dutifully contacted Wilson's staff to arrange for Wilson to sit for the portrait, he was told that the President was "fully occupied with Peace Conference Work." Colonel House, Wilson's "alter ego," did give Orpen a sitting, and House asked the artist if he had painted Wilson. "I replied 'No,' that the President had refused to sit, that he hadn't got time.... 'What damned rot,' said the Colonel. 'He's got a damned sight more time than I have.'" So House arranged for Wilson to sit, which he eventually did.
So he did the conventional paintings commissioned, and most eventually went to the National Portrait Gallery or the Imperial War Museum, but his most interesting painting got him into trouble. On the Western Front, he had begun to identify much more with the men who were dying than with the great figures whose portraits he was painting. Hence, one of his most important paintings of the conference was his To the Unknown British Soldier in France, which featured a flag-draped coffin against the gilt background reminiscent of backdrop for most of the Conference meetings. Originally, ghostly figures of soldiers from the trenches stood guard on either side, but the original painting caused much public criticism and controversy, and Orpen apparently painted out the offending figures in the late twenties--unfortunately robbing his painting of much of its original impact.
In any case, this conventional artist drawn into the war is an interesting study, and his impressions of the Conference, both in words and paintings, are interesting indeed.
See the Wikipedia entry for Orpen, though it is badly in need of revision and fails to mention the Conference at all, among other problems. Further, see the shorter but more informative Spartacus.net entry for Orpen. For a modern, informed appreciation of Orpen as an artist, with many photos and reproduced paintings (including a larger version of the January 18 plenary session at the top of this post), see the interesting blog series on Orpen at the blogsite "Articles and Texticles." For small collection representing a few of Orpens hundreds of paintings, see Wikimedia Commons. See also the interesting 1921 NY Times review of Orpen's memoir of the period.