These sites have images you can use without the guilt!  "Click" on the links...    

UNSPLASH  -  https://unsplash.com/

STOCKVAULT  -  http://www.stockvault.net/

PUBLICDomainPICTURES  -  http://www.publicdomainpictures.net/

MORGUEFILE  -  http://www.morguefile.com/

Wikimedia Commons  -  http://commons.wikimedia.org/wiki/Main_Page

IMAGE*AFTER  -  http://www.imageafter.com/

PUBLIC-DOMAIN-PHOTOS  -  http://www.public-domain-photos.com/

freeimages  -  http://www.freeimages.com/