For maximum flexibility, look for images that are in the public domain (not restricted by copyright). Wikimedia Commons lists a number of free and public-domain image sources. Check out Pixabay, Unsplash, and SnappyGoat. Europeana (Europe's digital library, museum and archive) offers many public domain images. The British Library has released more than 1 million images into the public domain. You can freely use, copy, modify, and share public-domain images, even commercially. While attribution is not legally required, it's good practice.
Images with a Creative Commons (CC) license are another good option. The specific CC license explains what you're allowed to do with the image. At a minimum, you must credit the image's creator. Wikimedia Commons features more than 71 million CC-licensed and public-domain images. Openverse is an extensive library of free stock photos, images, and audio, available for free use. All Openverse content is under a Creative Commons license or is in the public domain. You can also use Google, Flickr, and Bing to search for Creative Commons and public-domain images.
If you need to use a copyrighted image, track down the copyright owner and get permission. If you can't find contact information or licensing information for an image, avoid using it outside your course site.
Use images in the classroom
You may display copyrighted images in face-to-face instruction without permission from the copyright owner. For online instruction, following fair use guidelines, you can display legally acquired copyrighted images without permission when only people in your course can see them (for example on your D2L Brightspace course site). This includes slide decks, assignments, and other content. Just make sure your content isn't open to the world in something like Slideshare or Google Drive.
Instructors, include a notice in your syllabus that "the images should not be downloaded, copied, retained, printed, shared, modified, or otherwise used beyond the permitted educational uses."
TinEye Reverse Image Search
You can submit an image to TinEye to find out where it came from (and how it should be attributed), how it is being used, if modified versions of the image exist, or to find higher resolution versions.
You can directly paste an online image URL or you can upload a picture.
UA students, faculty, and staff have free access to Adobe Creative Cloud, which includes Photoshop and other design tools. Adobe Photoshop and other graphics software programs are also installed on computers in the Main, Science-Engineering, and Fine Arts libraries.
A number of free photo editing tools are available online, including: