When I first read your heading I thought "stripey carpet", but you already had that idea. I almost got one for my stairs (plain everywhere else) but chickened out. Wish I hadn't really, it would have lifted the look of the house I think. Alternatively, what about tartan?
We have oak flooring in the hell way it's all whites walls and paint work stair carpet is a light brown wool carpet. We have have a few pictures in duck egg IMO it looks nice and clean but doesn't feel cold
I thought I'd already made this decision - we've always wanted a stripy stair carpet but I can't find 'the one' as they all seem too muted in colour (the rest of the house is white and bright clean colours, but nothing muted). So I'm looking at plain carpets but I'm worried they won't work with the flooring. The hallway floor is Karndean French Oak which is light but quite warm in colour, so a beige carpet is going to make it look really yellowy, isn't it?