Also, it seems like "repeat" works (of the same artist or civilization) do not grant their normal culture/tourism. So if you stash 3 pieces from the same artist in a museum, you only get the culture/tourism for one. This also applies to the Medici Bank and the Hermitage. Interestingly enough, this limitation only applies to the Culture and Tourism yields, not Food/Production/Gold (which Kongo gets). Kongo gets full Food/Production/Gold even with works from the same artist!