Looking at the Museum map I see some space and landmasses that could house new museums for DLC. These are my top three ideas for location and theme:

1. There could be a museum situated at the base of an active volcano with lava rivers around it. The museum could initially focus on Geology exhibits, bringing in lots of new rock and mineral exhibit types. Large multi piece exhibits could involve building large rock formations in funny shapes. The expeditions would focus on traveling around the lava fields for new exhibits blown out of the volcano and could involve needing Janitors with the Fire Proof skill.

2. There could be a museum situated in an old Fort built on an old battlefield. The museum would initially be dedicated to warriors and warfare, bringing in new exhibits of weapons and armor from various time periods. Large multi piece exhibits could involve finding all the pieces to rebuild tanks and fighter planes and small submarines. The surrounding land could contain old ordinances (unexploded mines and bombs) and expeditions require Security Guards to defuse them. New bomb defuse skill?

3. There could be a museum situated in some large abandoned hangars or pit areas of a motor speedway. The museum would initially be dedicated to a variety of personal vehicles (antique cars, sport cars, luxury cars, and personal planes). Large multi piece exhibits could involve finding all the pieces to rebuild "experimental" vehicles with wacky shapes and designs (example a boat car or a flying car). The expeditions could travel to a huge junkyard to find the exhibits and require Janitors with the Mechanic skill.