Back in May Google added an integrated research tool to Google Docs. The research tool allows you to quickly find images, quotes, and links without leaving your document. Today, Google added the research tool to Google Docs presentations and drawings.
To access the research tool in Google Docs, Presentations, or Drawings just select it from the "tools" menu when you have a document, presentation, or drawing open. If you want to locate images that are licensed for re-use, open the "settings" menu at the bottom of the research pane and select "free to use, share, modify even commercially." Make that selection before conducting your search. If you use Chrome or Firefox you can drag images directly into your document, presentation, or drawing from the research pane.