What about stock photos? There is a license CC0 that allows content creators to use photos for FREE. Some photographers might require photography credit or if there are people in the photo a release form may be required. I am including a few sites that offer stock photos; however, make sure you always check for user requirements and type of copyright. Check out PEXELSpixabay, 500px , StockSnap , Kaboompics, Magdeleine , Freerange, UNSPLASH, Freeimages, and Gratisography .