When adding photos to your website, it is important to understand how to avoid potential legal issues. The following are some things to keep in mind:
US Copyright laws control how a copyrighted work can be used and this applies to the Internet as well. The Digital Millennium Copyright Act doesn't provide any new information about how to properly use someone else's photos or images online.
Did You Take the Picture or Create the Graphic?
If you took the picture or created the graphic then you probably own the copyright and can do whatever you want. Basically if you make it, you own it.
Attribution Does Not Make it OK
Taking someone else's image or graphic and then mentioning them or thanking them, linking back to their website, or any other type of attribution does not mean there was no copyright infringement, you still used their property without their permission. Copyright law gives the copyright holder the right to decide how their work is used and where their work is published.
Did you try asking them?
Some people will agree to let their image or graphic be used if you just ask them. But the decision should be theirs, not yours. It is true that they might say no, and the law will defend their choice.
Public Domain Images
There are millions of high-quality graphics and images available under Public Domain. There are many websites that link to images that are in the public domain and allow users to list images they would like to put into the public domain. You are generally free to use Public Domain images in any way you wish and usually you don't have to provide attribution. Check the terms of the site to determine what exaclty is required and be sure to follow the requested format.
Different Uses, Different Requirements
In some cases, you can use an image on your blog, but you may not have the right to use that same image in an email or video. Sometimes the restrictions depends on how many copies will be produced. Be sure to consider the use(s) granted by the copyright holder or license. A copyright holder may agree to certain uses but not to others.
Fair Use is a part of Copyright law that explains in what situations you're allowed to infringe someone else's copyright. It may sound simple, but it's one of the most complex parts of Copyright law. Copyright Fair Use for online images does exist but the criteria for qualification can be difficult to interpret.
Websites to look for images (be sure to observe all terms and conditions of each website)
Google has a search system that will allow you to find images that are "free to use or share".
According to official Google announcement
Today, we’re launching a feature on Image Search to help you find images that you can use for free, while respecting the wishes of artists and creators. This feature allows you to restrict your Image Search results to images that have been tagged with licenses like Creative Commons, making it easier to discover images from across the web that you can share, use and even modify. Your search will also include works that have been tagged with other licenses, like GNU Free Documentation license, or are in the public domain.
Here is the link: http://www.google.com/advanced_image_search
Be sure to set the appropriate setting under "usage rights"