This is a photo of the fixture in my room (ca. 1890-1910 early electric fixture), with the shades I mention, though as I said all the 90s ceiling fans in every other bedroom in my house has them. The shades on my fixture are reproductions, and I've found them elsewhere but as far as I know my parents got them at local places.

The shade with a 2 1/4' opening for electric fixtures
The shade with a 3 1/4' opening for gas fixtures
The shade with a 4' opening for gas fixtures

As for the actual lighting fixtures in the haunted mansion themselves, some of them I imagine are antique, but a majority are more likely than not custom designed modern fixtures with the intent of emulating people's preconceptions of gas/early electric lighting.

Hopefully that helped. =]