Website: https://www.flickr.com/creativecommons
Conditions: A range of access permissions as below. May be hard to find a specific image but is a huge and ever updating source.
Attribution means:
You let others copy, distribute, display, and perform your copyrighted work – and derivative works based upon it – but only if they give you credit.
Noncommercialmeans:
You let others copy, distribute, display, and perform your work – and derivative works based upon it – but for noncommercial purposes only.
No Derivative Worksmeans:
You let others copy, distribute, display, and perform only verbatim copies of your work, not derivative works based upon it.
Share Alike means:
You allow others to distribute derivative works only under a license identical to the license that governs your work.
Public Domain Dedication (CC0)means:
You, the copyright holder, waive your interest in your work and place the work as completely as possible in the public domain so others may freely exploit and use the work without restriction under copyright or database law.
Public Domain Workmeans:
Works, or aspects of copyrighted works, which copyright law does not protect. Typically, works become part of the public domain because their term of protection under copyright law expired, the owner failed to follow certain required formalities, or the works are not eligible for copyright protection.
Source: https://www.flickr.com/creativecommons
Free Academic Images 