would you consider a leather lounge?

I agree with the above statement but if you were to pick grey to go with it don't make it too dark you can add options of the emerald green on a lighter grey sofa in those colours of emerald green to tie it all together with cushions and throws I feel the sofa you already have is beautiful and should be focal point with the other taking a lesser focal but as stated tie it all together with that beautiful emerald green as accessories but don't over do it less is more so to speak take photos to show the people you want to buy another sofa from or even a swatch of the material. If you intend to buy a rug try for the lighter grey with hints of the emerald if you can find it, keep it soft and neutral but tie it in so that the whole area flows and looks classy, Good luck, PS some places let you pay for a rug and take it home to try and can return if it is not suitable so ask for that option.

You could try Kmart for some fun art work, or Bluethumb online.