1. An image display method, comprising: displaying a background image and a foreground image in an overlapping manner; determining whether to adjust a brightness of the background image; adjusting the brightness of the background image in response to a determination to adjust the brightness of the background image; and displaying the brightness-adjusted background image, wherein determining whether to adjust the brightness of the background image comprises: determining whether the brightness of the background image is to be adjusted based on a complexity of the foreground image, the complexity of the foreground image being determined based on a ratio of an area displaying a plurality of separated visual items in the foreground image to an area displaying the background image.