@stridah: No, darkening the floor will add some much needed contrast and the brighter walls and objects should pop more because of it. It's impossible to say for sure, without a visual, but it's certainly something to try. Because I agree, the details of the objects get lost with the floor. And it jives awkwardly with the rug too at the moment.
As for how to decorate the walls; you mention this is a Lord's Room and Royal's Guest rooms and such; does this lord have a colour theme, banner, logo, crest? You could add some banners themed to the family's crest if they have one or such. Fancy archway styled decals, panels, carvings, and reliefs and things are also pretty big in royal palace's and things. Rather than setting things on or in the hall - and decorating the wall itself.