Image search

When searching images via Google image you can change the settings to find images labelled for reuse.

Go to Google - Images, type in your search term, the click on Search tools.

From the drop-down menu under Usage rights choose the most appropriate option:

More about Image Search (all links open in a new window or tab)

Article:

http://www.openculture.com/2014/05/the-met-puts-400000-high-res-images-online.html

Guidance

http://oedb.org/ilibrarian/guide-little-known-image-collections-millions-free-hi-res-images/

JISC 'How to find images' guide:

http://www.jiscdigitalmedia.ac.uk/infokits/discovering-digital-media/finding/how-to-find-images/

Cartoons by Bob Pomfret (Oxford Brookes University):

https://radar.brookes.ac.uk/radar/access/hierarchy.do?topic=a7efa263-9613-2828-439a-da5e2293234a&page=1

Search for CC:

https://search.creativecommons.org/

Sites offering free photos even without attribution:

https://pixabay.com/

http://www.gratisography.com/

http://www.morguefile.com/

https://picjumbo.com/

http://picography.co/