Teal'c maneuvers the MALP into the barrier dome where the joystick on the MALP ends up not visible because it's outside the edge of the dome. The next shot where O'Neill says "nice", clearly shows the joystick. The subsequent shot of O'Neill and Teal'c has the joystick back outside the dome.
As mentioned in the DVD audio commentary at 6:30, a church was shown by accident in the deep background. It was considered unlikely that a church on an alien planet would also display a cross, unless Christianity had been introduced there from Earth, which had happened before (#3.8).
When O'Neill checks in with SGC, we see the camera pan to show us General Hammond and the monitor with O'Neill. You are able to see equipment (a step-ladder, some boxes and a few other items) in the hallway outside the gate room, through the window.
About 3 minutes, SG1 is in the toxic atmosphere which is moving towards the dome. There is a bare tree which is clearly a fake prop. The square base of it is obvious.
The area immediately outside the dome should be filled with the town's buildings that had only recently been lost as the dome shrank. The toxic atmosphere would take years to destroy them. All that remains of the closest ruins is steel trusses that would not have been used in any of the buildings in the town.