Showing images in in-person classrooms at Centralia College is almost always permitted without limitation by the Classroom Use Exception to the copyright law. This would include things like passing a book or other hard-copy image around the classroom or projecting an image onto a screen.
This exception ONLY applies to face-to-face classrooms. Instructors in online classrooms may still be able to display images but that use would need to be covered by fair use instead of the Classroom Use Exception.
Remember that the Classroom Use Exception permits the display and performance of copyrighted materials in the classroom but does not permit any copying. Any scanning, digitizing, or copying of images you want to do will need to be covered by fair use and, in many cases, it will be. It is important to remember, though, that it will not be in all cases.
If the copying (or scanning or digitizing) is legal (that is, it is a fair use) then it is likely that the subsequent display in the in-person classroom will be covered by the Classroom Use Exception.
Posting digital images (whether you digitized them legally or otherwise legally obtained a "born digital" image file) to a course shell would be a matter of fair use. This is true whether the image is posted alone or in a PowerPoint or other instructional material. This kind of use can certainly be fair but is not presumptively fair just because the use is educational.