Start the server with node memeplacer.js.
Your images will be available at e.g. http://127.0.0.1:8000/640x480
Fill the sources/ directory with images of various aspects. A suggested starting range is:
250x1000.1.jpg 330x1000.1.jpg 435x1000.1.jpg 574x1000.1.jpg 758x1000.1.jpg 1000x1000.1.jpg 1000x758.1.jpg 1000x574.1.jpg 1000x435.1.jpg 1000x330.1.jpg 1000x250.1.jpg
You can add variety by including multiple images at each size.