PIXABAY
Flickr Commons
Wikimedia Commons
Public Domain Files
PUBLIC DOMAIN PICTURES
PICDROME
GOOD FREE PHOTOS
SKITTERPHOTO
pdpics
PDPOSTER
PEXELS
UNSPLASH
Picography
PICALLS
Reshot
ISO Republic
Enciclopedia de Vida
LIBRARY OF CONGRESS
British Library (en Flickr)
PICKUP IMAGE
LIFE OF PIX
POND5 - FREE
WUNDERSTOCK
LIFE (en Google)
DUION / ARTE
VIINTAGE
THE FAMOUS ARTISTS
The Getty Art
FOODIESFEED
FOCASTOCK (by Jeffrey Betts)
LIBRESHOT (by Martin Vorel)
Free Nature Stock (Adrian P.)
Magdeleine (CC0)