Copyright
Remember, if material has been licenced for reuse, make sure you check the terms of use for any material you find, as these will vary. Some material may be in the Public Domain, where copyright has expired or been waived by the creator. As a general rule you should always acknowledge/attribute the creator of any material you reuse as best academic practice.
Indicators of free-use
Public Domain - Works in the public domain are those whose intellectual property rights have expired, have been forfeited, or are otherwise inapplicable. Public domain marked materials can be used free of any copyright restrictions or attribution. We would still recommend either attributing the work or keeping a record of its title, source, and copyright status in order to enable ease of re-use for future works and projects.
CC0 - Dedicating works to the public domain is difficult if not impossible for those wanting to contribute their works for public use. Creative Commons have created the CC0 licence to enable owners of copyright content, to waive those interests in their works and thereby place them in the public domain, so that others may freely build upon, enhance and reuse the works for any purposes without restriction under copyright or database law. CC0 marked materials can be used free of any copyright restrictions or attribution requirements. We would still recommend either attributing the work or keeping a record of its title, source, and copyright status in order to enable ease of re-use for future works and projects.
Credit
Icons used on this demonstration site are by Adrian Coquet, Evon, Ezgi Nazlı, Andrejs Kirma fron The Noun Project.