Watched "Walk of Punishment", wherein we first see Riverrun. The AV Club experts review gave credit to the show for succinctly demonstrating Tully personalities in the opening scene, wherein Edmure fails twice at lighting Hoster Tully's floating pyre and the Blackfish takes the bow to do it himself in one shot, just before the raft floats out of range around a bend. Once again, that is a scene from the book, not a show invention.
But the review also praises the small council seat-shuffling scene, and I pretty sure that one is a show invention. And I really liked it. Interestingly, the reviewer seems to suggest that Tyrion's act of dragging his seat to the end of the table demonstrates how, though he is still bound to them, he no longer feels love for his family after his father's rejection of his claim to Casterly Rock. I guess the idea is that he's literally getting as far away from them as possible. I actually interpreted it in a different way -- rather than being petty and going out of his way for a position near the head of the table, I thought he was making a point in setting himself directly opposite his father. Yes, the "power" position is the head of the table, but the head is just another end, right?
Still, the awkward tension of that scene was wonderful.