A picture speaks a thousand words.... which is why images are now a major part of webpages.
The Slideshow style Image gallery is a common control now found on many websites. It is a way of showing the maximum amount of images in a minimal space.
A gallery in which thumbnail images are shown. The main image stays static allowing the user to choose an image to view.
Mouse over Image
A simple control which changes when the mouse cursor is placed over the top of it. Can be used effectively by displaying a gray scale image which turns to colour on mouse over, or for displaying an image with a textual description showing up on mouseover.
Image Pop up
The image control is used to show a smaller image on the page, then when the image is clicked the full image is shown.