Google Images is a quick and easy way to find lots of images from web pages across the globe. But it only searches web content that it can find -- many images are actually hidden in databases or archives (whether freely available or in Cornell's subscription databases). The quality of images - size, resolution, description, usage rights - also varies considerably on the open web. Use Google, but don't rely on it for all image searches. Explore this page and Cornell's image databases for more high-quality options.
Flickr is a public photo-sharing site with billions of images. It is a rich resource to find images for your research (news events, places, people, etc.). Flickr users can opt to share their images with others under creative commons licenses (alternative to copyright).