When designing a poster (or any other material), it is your responsibility to abide by copyright law and academic honesty policies. That means:
- Properly citing ideas, images, quotes, etc.
- Understanding the copyright, licensing, and fair use of any materials, especially images, used in your design.
- You may want to search for open access or openly licensed materials, such as the image collections listed on the Open Access Guide. (Licenses vary by, and sometimes within, collections.)
- In many image search engines, you can search specifically for openly licensed content for reuse. For instance, search Google Images and then click on Search Tools and select an option from the Usage Rights menu.
- You can also search Flickr, and then choose a license (including 'No Known Copyright Restrictions').
- Fair Use covers a lot of education use, but you still need to cite it!
Scientifically Speaking: Tips for Preparing and Delivering Scientific Talks and Using Visual Aids by 
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