Images on their own are not accessible to anyone using a screen reader. As the
people putting content on the web, we can make images more accessible by
providing alternative text. This is such a standard that linters not only
flag <img /> tags that are missing the alt attribute, they also admonish
you for unhelpful description text like "image."
You can appease the linter and make your content accessible with some descriptive text:
<img src="some/image.jpg" alt="a graph with lines trending up" />When appropriate, you can also choose to include the alt attribute with a
blank value.
If an image is purely decorative, then we add alt="" to let screen readers know that it’s not important. But if an image is informative, then we need to be supplying a text alternative that describes the picture for anyone who’s using a screen reader or isn’t able to see the image.
Part of accessibility is not putting a bunch of noise in front of your users.
If the image isn't part of the content, use alt="".