I live near Washington DC, so I take my son to the Smithsonian museums frequently. I thought it would be great if they sold a one or two different "special" sized figures at each museum, so kids could actually beg their parents to hit up each gift shop to complete the collection.
Maybe they include a special sticker, or checklist to make them Smithsonian exclusive (then they could also extend to other museums such as the New York Nat. History museum)
Something like
Air & Space Museum - Astronaut
National Museum of the American Indian - Native American Chief
Natural History Museum - Caveman (and maybe a paleontologist or oceanographer?)
National Museum of American History - Civil War dudes
National Art Gallery - Painter with easel
Then there's:
Capitol Building - Revolutionary War soldier/ George Washington
White House - Abraham Lincoln
Archives / Mint - Patriot
We also have the International Spy Museum (awesome, but not part of the Smithsonian institution) that would be a great place for one of their spy figures. and the Crime & Punishment museum that could sell a gangster or police officer, and the Newseum that could sell a reporter/photographer.
Last year Air & Space sold a bunch of Future World playsets (including the big ones) but I didn't see any when I was there earlier this week. I think doing unique packaging or something for the museums would be great, and increase their "educational" appeal.