Everyone has objects that they place on tabletops to try to create that homey-feel. Framed photos, small mirrors, porcelain objects, and other purely decorative pieces fall into the category: "knick knacks". Its easy to over-use these items - which can make a space seem cluttered and messy, and its also easy to under-use them which will leave your home hum-drum and lackluster. However, I've assembled a few photos where the knick knacks were used just right.
It seems that the most aesthetically pleasing knick knacks are fresh flowers and vases and bottles of various sizes and colors.