Maybe wikipedia should have a "request a photo/picture" page, where people can put requests for photos to accompany articles. Especially when dealing with monuments/buildings/objects in museum.
Considering that Wikipedians are fairly widely spread around the world, it should be fairly easy to get photographs from a wide range of places.
With historical artifacts often the only photographs that are publically available are copyright to the museums (for instance I was trying to find a photo of the ancient board game "Royal Game of Ur" to use in an article, but the only ones I could trace were all copyright to the British Museum who own several of the few boards to have survived).
Imran