I have a shagpile rug over carpet. It looks good.

If you add a carpet over wall-to-wall, you need an underlayer between the two carpets. These are available wherever carpeting is sold. I have had Orientals on my wall to wall for years without any trouble of wrinkling or buckling. Just use the underlayer. Area rugs add color, define spaces and provide individuality to your space.

There are some pictures of it on this thread under my old user name. I think it works because the rug is practically the same colour as the carpet but just adds texture and depth.

[old living room thread[(https://www.houzz.com/discussions/how-to-finish-this-room-dsvw-vd~601103)