I realized as I was looking around my home that I must really like mixing patterns, as almost everywhere I look there are piles of pillows, cushions, and napkins with fabrics of different designs and colors. I also have used wallpaper with a pattern that I throw into the mix. I think it works because I always make sure that at least one color is repeated in at least two of the fabrics. Also I think it is important that the designs are of different scales.
Here are some examples of mixed patterns found around my home.