With a serious gaze as Douglas looked at the view, he nodded.  "I could capture some of the bookshelves and some of the windows behind you.  I think a book open there in front of you on the desk and perhaps some paper and a nice pen?"  He suggested, moving over to pick up a random book to open it to set in front of Tristan so show him what he was thinking.  He made it more at an angle as he had perhaps been looking at it to write something down on paper in front of him. 

"Maybe the pen in your hand.  Or hands folding in front of it like you just laid it down on the paper when someone came in to talk to you."  There were quite a few portraits in that kind of position that Douglas had liked.