This series of pages include examples of using alt text over the years, some good, some bad, some horrible enough for Lucy to scream. Please note: the pages depend on the Internet Archive for loading images, so they may take some time.
This is a gallery site for an artist's paintings and sketches. It includes hundreds of images that lack alt attributes. GalaxyGloo Gallery.
This web site shares a common pattern of using the article's title as alt text when there is no other description available. It's duplicative, doesn't describe why the image is included, but necessary when the image is the only content within a link. Yahoo Tech's use of duplicate headings
In this example from Food 52, the images are treated as decorative, which is good for unneccessary images, but fails when the image is the only element in a link and if the content could benefit from seeing what the recipe delivers. Food 52 empty alt.