This is our story arc
We did this a bit in Google in technology class. In the advanced search we chose free to use or share.
CC Search is a Creative Commons search engine that only searches out media you can use
Another site is Compfight
There are many others but these two should start you finding what you need. For every photo you select please copy the url to your presentation so we can use it in the credits.
Here are some example videos from the previous years to inspire you to find media and to give you an idea about what is possible when you want to make a difference.