To avoid this, there are a few ways you can find images (or other media such as songs) that are safe to use for newsletters, websites, etc.
The easiest way to find usable images is the "Usage rights" menu on Google Image Search results. After searching for something, click the Search tools button.
Then click Usage rights and select Labeled for reuse with modification.
This will filter your results to display only images that are likely able to be used. Remember that you still need to provide attribution, unless the image is explicitly tagged as Public Domain. Attribution can be as simple as providing a link to the original source.
For more information, check out the different types of Creative Commons licenses. For songs that you can use in projects check out Jamendo or the YouTube Audio Library.