I've had the opportunity with work to visit BNSF HQ in Fort Worth and their Topeka site as their on-site IT engineer and finally had the opportunity yesterday to poke around the museum and shop for a bit before I was pulled away for a meeting.
I was really impressed with how much history and antiques they've preserved - original artwork, rail cross sections, conductor lanterns, 1:48, 1:16 models, and some full-size streamlined passenger cars that they've transformed into conference space. The museum and shop are open to the public during the week, so if you're ever in the Dallas/FTW area, it's worth a visit!
I'm still trying to swing a yard/rail walk but from what I understand that may be a bit more difficult as they require FRA and OSHA safety certification, so I'm not keeping my fingers crossed.
Here are a few quick pictures I took with my phone (apologies for the poor quality or lighting - I couldn't nerd out too hard in front of my coworkers):