Is it good practice to set an image in a slide not as an img but as the background-image of the slide?

Question

css

In the docks , the image is set as img, and
I did just that .
However, the narrower the screen, the narrower the picture, and this spoils the impression of the site.
so I tried to set the picture not as an img, but as a background-image on the slide itself.
It looks better, but is it okay to do this. It's just that usually pictures are passed to slides as img tags.
Is it possible to get the result with the img tag as in the second option?