The main point of the promotion of any site, including free; an increase in its traffic and an increase in the number of visitors (potential buyers, subscribers, etc.).
The main emphasis (we will not take traffic from social networks into account) is placed on getting organic traffic from the search of the main search engines Google and Yandex.
I will notice in text search to move forward on high-frequency and commercial queries; the task is not easy, since the competition in it is quite tough, and it is much easier to do it in image search.
Website promotion with pictures.
In order for the images of your site to occupy good (top) positions in the search for Google and Yandex images, they must be large enough, unique, the photos must be of good quality (in this case, it is better not to save money by optimizing them and degrading the quality to increase the page loading speed ), well-filled attributes (most important: ALT; alternative name), describing what is displayed on it and located on a relevant page with quality content.
High-quality pictures will bring visitors not only from image search, but also from the main text search. For example, here is the result of a query for aquariums on Google.
As you can see, Google brought the pictures to the very first place, before the rest of the results, this is really a special case, he probably remembered that I recently used the picture search. And in the standard version, he had to place them somewhere in the 4th-5th place, as Yandex search did.
But after all, this is not bad at all, such promotion is free and does not require investments, but on condition that your image or photo attracts the user’s attention (this already depends on you); getting additional traffic from images to the site is guaranteed and the more images indexed by search engines will be on your site, the more visitors will be on it.