The Placeholder plugin is a quick and simple function for inserting image placeholders in your design or code. Add the shortcode in your post or page (or straight into your template) and get a customized placeholder.
An image placeholder is a dummy image designed to draw attention to the need for an actual image.
When designing WordPress templates and layouts, images to be used usually doesn’t exist at first as it is the layout that matters the most. However, the sizes for the images are usually preset and inserting some image placeholders help visualize the layout better.