Tired of COPYRIGHT issues? PIXABAY gives you hundreds of images dedicated by their authors for public use. “You can freely use any image from this website in digital and printed format, for personal and commercial use, without attribution requirement to the original author” (http://pixabay.com/). The works are under CC0 1.0 Universal (CC0 1.0) Public Domain Dedication scheme which means that “the person who associated a work with this deed has dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law” (http://creativecommons.org/publicdomain/zero/1.0/). You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission. You can contribute by adding your own photos.
The platform is absolutely free although you can make donations if you wish.
There is, however, one thing you should be aware of. The first images under SHUTTERSTOCK are not free. The pictures/cliparts underneath are (as shown in the screenshot).
Another way of finding free images attributed already is to go to http://www.nottingham.ac.uk/xpert/ and search for Flickr IMAGES. When you find a picture that you like, click on it and choose “get image with attribution” as shown in the screenshot.
You will be able to use this image without making any additional attribution as it is built in the image.