When we come to SEO, we usually think about meta tags, structured data etc. But what can a designer/HTML developer do with SEO? HTML developers are the one to start with SEO. They need to take utmost care when starting to build a web page. If they put an image names 1.jpg and the image is actually that of a car, it wont hep SEO.But for an article about a car, the image car.jpg helps a lot.

Google suggests to give realistic name related to the content of the page with included files like images. Google suggest to avoid

  1. Using generic filenames like "image1.jpg", "pic.gif", "1.jpg" when possible — if your site has thousands of images you might want to consider automating the naming of the images.
  2. Writing extremely lengthy filenames.
  3. Stuffing keywords into alt text or copying and pasting entire sentences.

Also when you use images to link to other pages, using ALT text will helps google to know what you are linking to. But avoid

  1. Writing excessively long alt text that would be considered spammy.
  2. Using only image links for your site's navigation.

So the key is, the SEO starts with the moment an HTML page is built.