Here is a list of free image sites on the web:
https://www.pexels.com/
https://burst.shopify.com/
Wikipedia:Public_domain_image_resources
http://memory.loc.gov/ammem/index.html
http://www.nps.gov/hfc/cfm/npsphoto2.cfm
http://memory.loc.gov/ammem/index.html
http://www.photolib.noaa.gov/
https://commons.wikimedia.org/wiki/Main_Page
http://www.photos-public-domain.com/
http://www.thepublicdomain.net/
http://publicdomainarchive.com/
http://www.publicdomainpictures.net/
http://www.lifeofpix.com/
http://skitterphoto.com/
https://pixabay.com/
http://nos.twnsnd.co/
http://jeshoots.com/
http://publicdomainarchive.com/
https://unsplash.com/
http://www.resplashed.com/
https://stocksnap.io/
http://www.gratisography.com/
http://negativespace.co/
http://www.splitshire.com/
http://littlevisuals.co/
http://deathtothestockphoto.com/
http://superfamous.com/
https://picjumbo.com/
http://www.imcreator.com/free
http://getrefe.tumblr.com/
http://freestocks.org/
http://snapwiresnaps.tumblr.com/
http://jaymantri.com/
https://stock.tookapic.com/photos?filter=free
http://picography.co/
http://www.freeimages.com/
http://www.morguefile.com/
http://raumrot.com/
http://magdeleine.co/
https://foodiesfeed.com/
http://thepatternlibrary.com/
https://www.wylio.com/
http://albumarium.com/
http://www.ancestryimages.com/
http://www.bigfoto.com/
https://freeimages.red/
http://crowthestone.tumblr.com/
http://cupcake.nilssonlee.se/
http://www.designerspics.com/
http://www.dreamstime.com/free-photos
http://epicantus.tumblr.com/
http://www.everystockphoto.com/
http://finda.photo/
https://foodiesfeed.com/
http://foter.com/
http://freenaturestock.com/
https://freerangestock.com/
http://www.stock-image-point.com/
https://www.goodfreephotos.com/
http://isorepublic.com/
http://kaboompics.com/
http://lockandstockphotos.com/
http://mmtstock.com/
http://moveast.me/
https://www.pexels.com/
http://photoeverywhere.co.uk/
http://photopin.com/
http://pickupimage.com/
https://www.flickr.com/photos/smithsonian
http://snapwiresnaps.tumblr.com/
http://www.splashbase.co/
http://www.splitshire.com/
http://startupstockphotos.com/
http://www.stockpholio.net/
https://stockphotos.io/
http://www.stockvault.net/
http://stokpic.com/
http://travelcoffeebook.com/
http://www.upicm.com/
https://images.nga.gov/en/page/show_home_page.html
http://digitalmedia.fws.gov/
http://www.freemediagoo.com/
http://creative-commons.deviantart.com/
http://www.fromoldbooks.org/
http://www.freeimages.com/
http://www.nasa.gov/connect/artspace/participate/royalty_free_resources.html
http://pictura.madebysource.com/