Are you actually talking about medieval hallways? My understanding of castle architecture from Gies & Toy on up is that they built rooms leading into other rooms, without hallways with rooms off the hall.

This is all fantasy art, and the source of inspiration isn't necessarily historical. All we can give you is guesswork. There was a great fashion for sticking up armour during the 19th century Medieval Revival fashion, like they built Gothic conservatories in new townhouses, as at Carlton House in London, or the whole building at Strawberry Hill. I would say that, like most "medieval" fonts, this habit is more Medieval Revival/Victorian Neo-gothic.

In the Middle Ages, they kept armour in the armoury. I have never read a mention in saga or legend of armour standing around handy. Negatve claims are not really sourcable.