I have a quick question, which is semantically more correct:
Placing an image like this <div><img src="" alt="" title="" /></div>
Or by using CSS as background-image?
That surely depends on your requirement.
If that image is for styling your page, then it should be served as a background.
If that image has some other purpose in your document, say a logo, title, icon, picture to be displayed in a gallery page or in a profile page etc, then it should be served as an img, so as to be visible even in the naked css