A system and method for detecting useful images and for ranking images in order of usefulness based on a vignette score describing how closely each one resembles a "vignette," or a central object or image surrounded by a featureless or deemphasized background. Several methods for determining an image's vignette score are disclosed as examples. Variance ratio analysis entails calculation of the ratio of variance between the edge region of the image and the entire image. Statistical model analysis entails developing a statistical classifier capable of determining a statistical model of each image class based on pre-entered training data. Spatial frequency analysis involves estimating the energy at different spatial frequencies in the central and edge regions and in the image as a whole. A vignette score is calculated as the ratio of mid-frequency energies in the edge region to the mid-frequency energies of the entire image.