It's not set lighting. These pictures were taken by a camera phone after the crew had wrapped on the set. A camera phone is typically not good enough when it comes to white balancing, so what you get for tan and brown is gold under the stage house lights. If there were stage lights, kinos, etc...
My recollection is that it was for the Superbowl Special that year. If you remember they had a big float with an Indy look-alike and he was handed a script for that event, and thus he stepped out.
On a film set the armorer, or sometimes the prop master holds the firearms unless they are needed in a scene. No one is allowed to walk around a set with a firearm unless cameras are rolling, everyone takes safety seriously. So far you've seen only ONE publicity shot that was between shooting...
That set is 100% for National Treasure 2. This was a small piece built in addition to the large set they built at the Falls Lake location on the Universal Studios back lot. They moved this piece closer to the Mummy portion of the tram ride up against the tree-line to make way for the actual...