Pexels.com is the world’s first inclusive free stock photo & video library. You can use the photos and videos available, anywhere—in your brochures, handouts, documents, websites, presentations and blogs—just anywhere you wish to use them. All photos and videos on Pexels are free to use.
Attribution to the original photographer / videographer is not required, although such attributions would be appreciated, for obvious reasons. You can modify the photos as you like. Just be creative and create a work of art; there are no restrictions to the modifications either!
You may use the photos for commercial purposes as well. What is not allowed is to publish pictures of identifiable people in a bad light or in a way that is offensive. You may not sell unaltered copies of the pics or videos, without modifying them first.
A very useful site to embellish your creativity, one pic at a time!