Image search engines are a relatively new idea that can be used in many areas in the world. They can help in searching for general categories of a topic, as well as patterns or specific ideas.
Text-bases image searches are the most common type that have been implemented, but content-based image searches will surely be available for public use in the foreseeable future.
Both Google and SIMPLIcity are strong steps in the right direction of where image search engines should be headed. Google is both reliable and fast, and SIMPLIcity's functionality of matching image content is much more precise and reliable of an idea than searching for surrounding text.