Here's a list of online sources that will enable you to download free images:
albumarium |
burst |
flickr |
freeimages |
getrefe |
gratisography |
imagesource |
imcreator |
jaymantri |
kaboompics |
lifeofpix |
littlevisuals |
morguefile |
nos |
pexels |
picjumbo |
picography |
pixabay |
stocksnap |
unsplash |