When Lucas removes the bandages and tries to see for the first time, Marks asks him if he can see. At this point, Mark is looking directly at Lucas but when Lucas focuses in on Mark, Mark is looking off to the side. Mark should have been looking directly at Lucas (or in this case, the camera) since he had just spoken to him and was waiting to see if Lucas' sight came back.
When Micah goes into the saloon to talk with Jack Solby, the bar is along the side of the wall. In all other shows the bar, in North Fork, is against the back wall.
The background scenery behind Solby near the end, when he arrives to shoot Lucas, has some near vertical lines just to his right that make it pretty obvious it's a painting.