seo – change picture name or create a picture sitemap? Or both?

The Environment is a classifieds site offering products with descriptions, titles and photos. With the exception of images, all data is stored in a MySQL database.

Although there are friendly titles of classifieds and it is relatively easy to link to them, all images are saved with randomly generated names (something like d6as897d6ad67a5s7da8d56sa7d.jpg).

The question is, for SEO, PAGE RANKING and SERP, which is the best and why?

  • Change the image names from random characters to classified titles.
  • Create image sitemap;
  • Both.

What are the advantages and disadvantages? And why not choose the other options? Are there any other alternatives that I have not mentioned here?