But how would you identify horse-carts in westerns, what makes and models would you list them as? Will IMVDB include shopping trollies as well?

Basically I think an Internet Movie Aircraft Database would be for people who are interested in AIRcraft not spacecraft, there's no air in space (although perhaps it could include the Space Shuttle because that can still fly within the Earth's atmosphere). All the people who want to see fictional spaceships (and I do like Star Wars and other sci-fi stories) can look at some of the MANY existing internet sites that features spaceships from these films and TV shows.