"The Virtual Tour of the Acropolis monuments consists of high-resolution gigapixel images and panoramas of the most prominent monuments - the Parthenon, the Propylaia, the Erechtheion and the Temple of Athena Nike - as well as detailed photographic displays of selected views from the outer surface of the ancient walls surrounding the hill."
Artstor is an online repository of more than a million digital images relating to art history, covering a wide range of time periods and cultures. This is the major database for images of art objects. Thumbnail images from Artstor are included in ArticlesPlus, with links to the full records in Artstor itself.
There are a number of videos on Youtube which can help you learn to use ARTstor effectively.
Flickr is a vast photo-sharing site. You can search the whole site and/or explore some of the sections listed below (originally posted at AWOL: the Ancient World Online) which are devoted explicity to the ancient world.