Using the Image From free Source Providers like unsplash.com

This is the website which provides millions of the free image with copy paste right to you.
You can get image of you choice and as per your desire and requirement. it does not charge anything to you.
Though you need not provide the image source but as a good practice you should provide the detail under image source. it will gives exposure to the Photographer.
It provide you all type of the images with detail of the Image also.
You can also view the detail of the image , how popular it is and all that.
For example following image from above site

image source:https://unsplash.com/photos/6W4F62sN_yI
This image is taken from the above location.
image Views: 3,925,178 over the above site.
camera as per the site: Canon EOS 5D Mark III
aperture: ƒ/2.8
focal: 200.0mm