An image placeholder is a dummy image used to draw attention to the need for an actual image. The most common image placeholder is a grey background with mountain & sun icons. You can also design your own version of image placeholders in line with your branding.

Image placeholders are used in web and app design when the final images aren't available. For example, you can see them in wireframes or early mockups and prototypes. Another application is to use image placeholders in skeleton loaders to hold space for images while the page content loads.