For ALL images, 1440px x 400px is the OPTIMAL image and will fit the class banner area and will be sized perfectly.
For example, see this image on this class https://www.learnitlive.com/Class/LearnItLive-Platform-Orientation/15804 - it fits exactly.
Now, if you don't want to take the time to size your images to 1440x400, and many headshots aren't easily formatted this way, then you can upload other resolutions knowing that they will be cropped.
The one thing to aim for is a width >= 1440 px the height 600 to 800 px (about half the width) and the focus of the image around 1/4 from the top of the image. Vertically oriented images will be problematic.
Here is an example of what we mean. Check out how this image appears on this profile.