Image Quality & Uniqueness Can Affect SEO. Generally, you want to add images to content to make it more engaging for the reader, and to break up large blocks of text. This is great for SEO. You can get free images from websites like Pixabay. They won’t harm your website optimization because of the source. However, it’s better to avoid poor quality images, and images that are overused.
These kinds of images get poor engagement, and Google’s algorithm is able to sense this. Additionally, it will sense that other websites are using the same image. So, while you won’t get penalized, you also won’t get a bonus Google Images listing, and you’ll miss out on that traffic.
Also keep in mind that there is a small risk that the images uploaded to websites like Pixabay are in fact copyrighted. When that happens, you may get cease & desist letters in the mail, along with demands for royalty payments.
If you can afford it, try a paid image source. Fewer people will have legal access to that content, making it rarer. Plus, it’s likely to be higher quality, and more engaging.
If you don’t have the budget for paid images, then free ones are the next best option. They will still enhance your content, and they’ll break up large sections of text to make it more readable. Google loves this.