Most images you find on the Internet, in books and elsewhere are protected by copyright. The act of creating something automatically gives it copyright protection. For example, you own the copyright in the photographs you take with your smart phone.
The use of copyright protected images in student assignments and presentations for university courses is covered by Copyright Act exceptions for fair dealing and educational institution users. The fair dealing exception allows you to use excerpts of copyright protected material in certain circumstances without asking permission. The educational institution exceptions permit specific uses of copyright protected material by instructors in the classroom. See the FAQ "Is there a limit to how much I can copy?" for a simple break down of how much you can copy under SFU's Fair Dealing Policy, which is the University's guidelines for working under fair dealing. See the Copyright Infographic describing both fair dealing and the educational institution exceptions for instructors, to find out what you can do when presenting to your class, handing things out to your classmates, or otherwise acting like an "instructor" in your course.
In general in your course assignments you can, under fair dealing for purposes of research, private study and education, use one entire image from a compilation of images (e.g. a gallery of images on the Web, a coffee table book), or up to 10% of a stand alone image (an image that is not part of a larger compilation but is on its own such as a photograph pinned up on your wall). The educational institution exceptions will allow you to display an entire work (even a whole stand alone image) in the classroom (e.g. in your PowerPoint slides), but not to hand out copies.
In certain circumstances you may be able to use more than a "short excerpt" (e.g. 10%) of a work under fair dealing. SFU's Fair Dealing Policy sets out "safe harbour" limits for working under fair dealing at SFU, but the Copyright Act does not impose specific limits. See the FAQ "What is fair dealing and how does it relate to copyright?" for more information. If you want to use more than is outlined in the policy, and your use doesn't fall under the educational exceptions, contact the Copyright Office to ask for a fair dealing assessment to be performed.
It is also an excellent idea to look for images that come with re-use rights, which you can freely use within the limits of any license terms. Examples are materials posted to the Web under a Creative Commons license, or materials that are out of copyright and now in the public domain. You can search for such material using the Creative Commons search engine.
Please contact the Copyright Officer at firstname.lastname@example.org if you have questions.