I have three plain gray pillows in my bedroom that this would be perfect for! (thehappyhousie.porch.com)
They have silver studs throughout the arms and base which adds a modern touch but they're super comfy and roomy and come with massive gray pillows to match. (theglowingfridge.com)
And although you wouldn't think gray pillows would work on a gray sofa, they really do. (inspiredbycharm.com)