My sewing room has one wall with black and blue wallpaper, two walls darkish blue and one light blue. Only because it's actually my sister's bedroom that we took over when she moved out! I don't find it a problem at all, but I've never had cream walls, so there might be a huge difference that I'm just not aware of!
If you're too nervous to go ahead with the sage, try doing it all cream and then make a large wallhanging for one wall to brighten it up. Then you can change it if you fancy a different colour :-)