PDF Tagging Images
Tagging images in a PDF needs a different technique to most of the text tagging. This is because you can't highlight an image and create a tag from selection, as you can with text.
To tag an image, you need to go into the Reading Order pane and identify the image as a figure first. Then it should appear in your tags list. However, where it actually appears is anyone's guess! You might have to search for it and then move it to the correct place in the tags list.
The following video shows how to create an image tag and give it alt text.
In a PDF, decorative images are called artifacts. These are created differently in the Reading Order pane. You need to select the object and then mark it as an artifact. Artifacts do not appear in the tags list as we don't want a screen reader to read them.