1. A method for generating thumbnail images, comprising the operations of: extracting a plurality of pixel-level features from each of a plurality of source images, wherein each of the source images is associated with a thumbnail created by an editor; generating a plurality of unique bounding boxes for each source image; calculating a plurality of region-level features for each bounding box, wherein each region-level feature results from the aggregation of pixel values for one of the pixel-level features; learning a regression model, using at least the calculated region-level features and the thumbnail associated with the source image; and choosing a thumbnail from a plurality of unique bounding boxes in a new image, based at least in part on application of the regression model, wherein each of the operations is executed by one or more processors.