How can I find Images that can be reused while not violate copyright?

There isn't any way to be 100 percent sure, unless you have an authentic, original work that was published in the USA prior to 1923 (no longer copyrighted), or other works for which the copyright has expired or never existed. Works of the US government are not copyrighted under US laws. There are millions of copyright-free images, meaning you can do what you want with them, but it's up to you to find them and at least try to verify their publication date and country of origin. Copyright duration varies by country, although the international standard is "no less than 50 years", typically measured from date of publication or from the author's death.

The vast majority of what you find on the web remains copyright protected. All works are protected automatically unless the copyright holder has very specifically dedicated the work to the public domain, or provided something like a Creative Commons license.

You're best off trying to find a site that clearly hosts royalty free images, rather than searching via Google. Most of what you find on Google is actually still protected.

There are few if any images that can be used "freely" for commercial purposes.

Try searching flickr, go to advance search, then check off "Creative Commons only." Additionally, you can google "royalty free" or "Creative Commons" stock photo websites.

GOOGLE IMAGES