No matter where you search--Google Images, Flickr, TinEye, OtisDID, BePress, etc.--ask yourself these questions:
Credible (with a vested interest): Museums, galleries, artists’ websites, Artsy
Mixed bag: Wikipedia, artist appreciation sites, news outlets
Be wary: Stock photo agencies, Pinterest, Amazon, blogs
Sometimes you need a quick image for reference. Other times you may need a high-resolution image for printing. Find the image that best meets your current needs.
Evaluate the image in terms of quality
The Art of Reproduction recreates famous images by splicing together images found on online.
You can see differences in:
The quality of images in Wikimedia Commons varies widely. Usually, there are multiple versions of the same piece posted. For example, go to The Starry Night by van Gogh.
Follow the link to source website, especially for works of art. You may find a better quality or zoomable image, such as The Steerage posted on the Getty Online Collections.
Need to identify an image? Looking for a better file or a different view? Use a reverse image search.
TinEye.com is a reverse image search that allows you to sort and filter results in a variety of ways. It is especially good at matching stock images.
It also has a comparison tool to show you how different or alike the result matches your image.
Write down where you found an image. Add it to your research log on Gdoc, Evernote, Zotero, Word, etc. Do not rely upon google searches. You may need this information in the future.