The listed resources offer image collections that fall into one of the following categories:
photo credit: "Symmetric perplextion" - Snowdonia national park, Wales via photopin (license)
Google Image search may bring you back thousands of related images it can also be very difficult to wade through low quality or restricted images.
You can filter your search results by size, colour, format, and usage rights. Click "Search Tools" from the top of the image results screen to access these filter options.
When browsing through the resulting images use the option to "view page" to access the image from the original source. This will help in obtaining the correct licensing, attribution and citation information.
Many libraries, museums, and government organisations have image collections available for public use hosted on their websites or image sharing services such as Flickr.
For the purposes of study and research, "Fair dealing" allows students the rights to copy portions of work, including images in certain circumstances. For more information on this please consult the Copyright for Students webpage.
Scanned images still require reference entries and attributions.
Before taking and using photographs in a university assessment you need to consider the issues associated with taking photographs of people, buildings and artwork. The Copyright Guide to Photography has some guidelines on photography in these circumstances.
Stock image sites offer images for purchase. You should always check a photo's license before using it to ensure you comply with any conditions or costs associated with its use.
Most stock images will be offered under one of these two licenses: