The painting before which Walker and Underwood are contemplating is "The Avenue in the Rain" by Childe Hassan, painted in 1917. It's part of the art-collection of the White House. President Obama decided to hang it in the Oval Office in 2009.
Reg E. Cathey & Mozhan Navabi also appeared together on an episode of The Blacklist - episode 3.16, The Caretaker (No. 78) (2016).