Some embodiments provide an image-viewing application. The image-viewing application displays a thumbnail display area that includes several thumbnails that each correspond to an image. With a set of at least one thumbnail selected, the application receives selection input over a particular unselected thumbnail in the thumbnail display area. When the selection input lasts less than a threshold duration, application selects only the particular thumbnail and displays the image corresponding to the particular thumbnail in an image display area. When the selection input lasts at least the threshold duration, the application adds the particular thumbnail to the set of selected thumbnails and displays the images corresponding to each of the selected thumbnails in the image display area.