Recently I have been running reports on an older website to see where there are quick wins to be had at improving the site.
Something that greatly benefits accessibility and has an added effect of being better for SEO is to have relevant alt text associated with your images.
If you are using Rails this is easy to implement.
You may already be familiar with using
image_tag("my_image.png") which is smart enough to go and look in the assets directory for your image.
This same method accepts an alt parameter, this means that;
image_tag("icon.png", alt: "MyInc Logo")
<img src="/assets/icon.png" alt="MyInc Logo" />