An image generation device includes one or a plurality of processors executing: communicating with a first terminal device executing a first application program and a second application program; acquiring first image data representing a first image displayed by the first terminal device according to the first application program and first resolution information representing a resolution of the first image; acquiring second image data representing a second image displayed by the first terminal device according to the second application program and second resolution information representing a resolution of the second image; deciding a layout for arranging the first image and the second image in an output image, based on the first resolution information and the second resolution information; and generating an output image having the first image and the second image arranged therein, based on the layout, the first image data, and the second image data.