Retro is a term referring to the past but when it comes to interior design that usually mean other things too. In interior design retro look is usually a mix of 1970s and futuristic elements. If your interior looks quite classic and traditional you can add retro feel to it with modern and even futuristic looking furniture. In case your interior is contemporary to make it more retro you can add such things as retro furniture, vintage and antique decor items, colorful paintings, studded sofas and so on. In the result you can get a really beautiful living room or even use these ideas for other rooms.
Source: decoratualma, flickr