Will Google pick up images you include in a div tag? The answer, at least from Google's John Mueller, is likely no - Google Image search will not pick up those images. John did suggest to the SEO that they can and should test it to be sure but from what he understands, Google won't pick up images directly in a div tag.
The div tag is nothing more than a container unit that encapsulates other page elements and divides the HTML document into sections. Web developers use div elements to group together HTML elements and apply CSS styles to many elements at once.
If you do something like in the tweet below, Google Image search won't likely find it and rank it:
I'm pretty sure we wouldn't pick that up for image Search, but try it out :-)
— John ☆.o(≧▽≦)o.☆ (@JohnMu) June 6, 2018
Google has a similar issue picking up images in background CSS.
Forum discussion at Twitter.