It is difficult to view the image if the size of the image is very large.
Select an image, right click on it, click "Restore to Original Size" on pop up menu. OneNote will restore the image to original size. Shortcoming: this way will change the note to view an image.
Save image as a file to disk. And using your favorite image viewer to open to view.
Shortcoming: this is too much steps, and it's not convenient.