Oh phooey, forget you ever heard the word "rules." It's your house, your fabric, your time so make whatever you want and display it anywhere you want. I guess at some point in my life that might have mattered to me, but no way does it now. The first thing I thought about when I read your post was that I grew up in a house of six children. You can guess how much we had that matched. And I have wonderful memories of being surrounded by unmatched things.