One part of web design is page decoration. Try to make your website's individual pages have some character. Sometimes one of your decorations might be an image, but sometimes it's just anything so that the visitor doesn't think your page is unfinished.
Page decorations can range from vintage to modern and they are generally expressive of some kind of personality. In a perfect world, they express personality related to the page, but sometimes there is almost literally no artwork that can do that. So you just add something to spice up the reader's experience and make it a little more welcoming to read the content of your page.
Think of yourself as Jennifer Aniston's character in the movie Office Space and choose just one or two pieces of flair. Your visitor may not love your flair or comment on it, but whether they know it or not, their experience will be brighter for your effort.