Google Images can also be a source for images, but you will need to use specific terms in your search.
Such as: ancient greece amphora panathenaic
ARTstor provides a broad and deep general collection of images of world art and architecture, as well as special collections including Native American, Asian, American and European art.
Hallie Ford Museum of Art Ancient Collection includes over 100 objects, including Egyptian funerary objects, statuettes of Egyptian gods, Etruscan bucchero pottery, Greek black figure pottery, and Roman glass. Type in the word Greek in the Search box to find digital versions of these objects.