An oriental-type rug would work very well if you choose colors that are present in your sofa fabric. I wouldn't choose something too geometric but on the other hand would not go with a very realistic flower pattern either because that would be rather boring. The size of the main elements in the rug should be either larger or smaller than the sofa fabric. The main factor as stated is to repeat one or two main colors from your sofa in the carpet. Traditional English interiors have used floral chintzes and oriental rugs together for ages with great success.

Here's a chair done in a Laura Ashley fabric, sitting on an oriental rug. I think it works because the chair fabric is just two colors, cream and blue. Maybe getting a rug that is not multicolored, but rather two colors, would make it easier.

There is an old Laura Ashely book called Decorating with Patterns and Textures. It might be useful to look for it at the library or on half dot com.