Lazy Loading vs Validator. Are there techniques for layout validity when using Lazy Loading?

Question

HTML

Hello.
On my sites, I use the "slick" carousel with the Lazy Loading feature. This allows mobile devices not to load all the pictures from the big carousel. But this method also has a big minus, because the src="" attribute is not used, which in turn affects the validity of the code, and, accordingly, organic results in search engines. Please tell me, are there any techniques to leave the Lazy Loading image, while the layout was valid? Or maybe there is already another similar slider (adaptive + touch) in which this technique is solved differently? Thanks for the help.
<img data-lazy="img/lazyfonz1.png"/>

Answer 1

In src, specify a dummy image ala

<img src="http://placehold.it/250x250" alt="Товар">