Using copyright images can violate legal rights of the owner which may result in strikes. However it is quite friendly to use non-copyrighted images in blogs, websites, presentations, etc.
You can always use copyrighted images with proper permission or a valid licence.
There are lot of websites to find non-copyrighted images but here are steps to find them on google image.
How to find copyright free images
Google images contain both copyright and non-copyright images. There is a way to filter all non-copyright images. Below are steps to find them.
1. Go to google and search.
2. Select Image option
3. Click on Tools and select Creative Commons licenses for Usage Rights menu
4. Select Image and right click to save the image
This feature is not available on duckduckgo.com at the moment but here’s a way to access google easily from duckduckgo
Just add a !g at the end of your search to access google.
There are some downsides of using using non-copyrighted images like Poor quality(most likely), you will see them more frequently used by people on there blogs or websites or videos which fails to make things distinct.
After all it all depends on needs of a person or organisation. Using copyrighted images with proper permission is better then using non-copyrighted once as you’ll encounter less people using them.