I have noticed an increasing trend to use the property background-image instead of inserting a direct <img> tag.

This is actually detrimental to the page and website. Think about it carefully. Let’s say that (as a lot of sites do) the site uses a <h1> tag but instead of putting the site’s name in, they leave the tags empty and use the background-image property to insert an image in place of what would ordinarily be text. What this does not insert into the page is the alt attribute of the <img> tag. The search engines look for this attribute, and look for the <img> tag too, and link the name of the graphic with the content on the page.

When the designer uses the background-image property though, the alt attribute will not exist, nor will the name of the img since an <img> tag won’t exist either.

I’m not sure where this trend has come from for using the background-image property over the <img> tag, but it’s unhelpful, especially if a newer generation of designers think it’s a preferable method of placing images on a page. It’s not. The search engines will simply not see the image, and so ignore any information that an <img> tag could pass along for SEO purposes.