Dummy Images provides functionality for generating image placeholders which can be used for various purposes – set temporary feature images, filling blank spots, test and play around with different image sizes and etc.
The plugin gives you the option not only to generate a blank image but to customize it. You can easily select the dimensions, background color, text and text color of the dummy image.
Te puedes descargar este plugin para utilizarlo en tu instalación autoalojada de WordPress.