I'm not as big a fan of such places as she is, though I found the Franklin D. Roosevelt library (when I visited in 1971) and the Ronald Reagan library interesting. One item that struck me at Lyndon B. Johnson's library was a portrait by Ft. Worth artist Wayne Ingram. It was painted in 1968, LBJ's last full year in office, but was not the "official" portrait of the man. Because it was unofficial, its style was freer like some society works done by the painter (about whom I found next to nothing on one of my typically brief Google searches).
The multiple-views approach Ingram used can be a bit contrived, but is a huge improvement over the Cubist conceit that Picasso and the rest were providing simultaneous multiple views in a single depiction. Ingram includes two ghosted portraits of LBJ that do not detract from the primary portrait. His painting style is a skilled blend of naturalism and abstraction that also borders on being contrived. Nevertheless, the painting is striking.