Everyone loves free CC0 images to use personally or commercially.
In short, a CC0 image is any image that is free to use personally and commercially. You are allowed to modify, copy and distribute the image without asking for permission or linking through to the source (image attribution). Most of the image sources below offer CC0 free images. Please take care when downloading.
There is such a thing as free lunch
Most of the below websites do place small restrictions on the way or manner in which the images would appear. Essentially, images should not appear “in a bad light or offensive manner” (which is subjective to the user and viewer) or that you cannot redistribute the image. Make sure that you read each website terms, conditions and licence agreements before you use any image. For more information about CC0 visit the official Creative Commons (CC) page.