The King is with his herald, the March Pursuivant and standard bearer Sir John Scrymseor, Constable of Dundee*. In the background is Threave Castle as it is today, then the stronghold of the Black Douglases in the South West and the scene of their last stand in 1455.
* Please note that I am not entirely sure of the titles for James II's herald and standard bearer at this time. It's an educated guess based on the sources available to me. Please let me know if it's wrong!