SEO for images

The image should be relevant to your article. The name of the file should be relevant to the content of the image and be of the form: main-keyword-secondary-keyword.jpg

The image should be served at the size it will be displayed

Use srcset for responsiveness

Serve compressed image if possible in webp.

The number one SEO factor for images is the file name. It should have a structure such as keyword-secondaryword-index.jpg

Use structured data for your content and include the image :

<script type="application/ld+json">
{
  "@context": "http://schema.org/",
  "@type": "Product",
  "name": "Reguleeritav kontorilaud",
    "image": "https://www.example.com/images/category-productname1.jpg",
      "description": "A compelling descritpion",
      "offers":{
    "@type": "Offer",
    "priceCurrency": "EUR",
    "price": "575"
  }
}
</script> 

Alt description and title should contain your keyword but it doesn’t seem to be a major ranking factor.

My hypothesis is that the content of the page itself gives the search engine enough context about the image. An image that is unrelated to the text around would be out-of-place and that might be a bad signal. The name of the file, if properly done contains already more specific information about the image. Alt and title are meant to be used if picture does not display and for assistive technology respectively.